A funny thing happened during the tax rebellion here: the Dade Tax Revolt committee, which wanted to cut real estate taxes in half, may get far more than it bargained for, by accidentally slashing taxes by more than 99 percent.

Such is the difference two little words can make when they are part of tax rollback petitions signed by 15,000 seething taxpayers trying to force their own local Proposition 13. Instead, what it appears they're going to get will be, for reasons to be explained later, "Proposition .004."

Metropolitan Dade County officials use words like "disastrous" and "staggering" to describe the difference the two words may make. Not that they would have been happy with even the 50 percent chomp.

Even the measure's framers are unhappy. "We didn't want to wipe 'em out," concedes tax-axe-wielder Harry L. Wilson. "We just wanted to tighten their belts for a year."

County Manager Merrett Stierheim today unveiled a budget that doesn't exactly wipe out county services to a million people in 27 municipalities but does call for substantial cutbacks in crucial services and severe reductions in others.

For openers, he predicted that each locality would have to assume its own murder and robbery investigations, one prison could be closed, with some 500 prisoners released prematurely, and work release programs would be abolished.

Divorced mothers would not get assistance in receiving child-support payments, super market scales would go untested for accuracy, bus service would be cut by 80 percent and many riders forced to other kinds of transportation.

An estimated 22,000 street lights on 400 miles of main roads would be flicked off for good, abandoned cars would remain where they were left and health services would be severely cut, including the closing of two nursing homes.

And on and on.

In short, said Stierheim, as the county surrendered these functions, the result would be "human suffering, massive inconvenience and deterioration of our public facilities."

"They're going for broke" trying to scare up a defeat of the tax cut referendum, Wilson, twilson, who claims county officials are to blame for the vote on a 99 percent tax cut instead of a 50 percent one. "They're playing Russian Roulette," hoping the tax cut will be defeated out of fear, he said.

Wilson got into all of this a year or so ago when his monthly real estate tax payment began exceeding his mortgage payment. By last October, Tax Revolt had filed its 15,000 signatures (10,000 were needed) calling for a referendum on a 1979-80 Dade tax rate of "4 mills per $1,000."

Everybody in and out of county government kind of assumed that meant $4 for each $1,000 of value of a given property. That would be half of the current $8.096 tax rate. But then someone realized that tax rates are usually set in mills, period; mils "per $1,000" (the two little words) is something else, and far less. What it is, is $.004 in taxes for each $1,000 of property valuation. Hence, Proposition .004.

Wilson maintains that the county knew darn well what he was doing and should have corrected the referendum ballot. Stierheim says the county doesn't have the power to change the wording on the petitions, so on Sept. 18, area voters will face the question in a referendum on what is apparently a 99.95 percent property tax cut.

What that means is that instead of collecting $173 million in real estate taxes, Metropolitan Dade County would collect a bare $91,000. The result would be that an estimated 9,000 of 14,000 employes would be fired, with minorities and women, the most recently hired, leaving first.

Because the county has other sources of revenue - fees, federal revenue sharing and state funds at its disposal - the overall impact on spending would be far less than 99.95 percent. The metro Dade budget would shrink from $331.4 million to $155.9 million - a net loss of $175.4 million.

The matter, however, is pending before the courts.

But already it is causing disruption. Merrill Lynch Pierce Fenner & Smith told the county yesterday it is backing out of a $67.5 million bond purchase because of uncertainties caused by the tax vote.

One source here, however, also noted that bond interest rates have gone up since the brokerage firm agreed to buy and resell the bonds. "That's a quick amount of money," the source said.

But the firm's decision could delay construction of an obstetrics wing at Jackson Memorial Hospital, a new library, two museums and 27 other projects that the bond sale would have funded. The delays could add $4.7 million to construction costs because of inflation.

Meanwhile, Stierheim said today, "there is a level of frustration among the American people, and there is always a danger people will give vent to that frustration in the voting booth. But I think the voters in Dade county will not." CAPTION: Picture, Merrett Stierheim: "They're going for broke...playing Russian roulette." AP