Despite President Carter's decision to put his adminstration firmly on record against rising Cuban intervention in Angola, he still faces divided counsel based on conflicting evidence of just what Cuba really is doing in southern Africa.

The conflict of factual evidence - in this case evidence adduced by United Nations Ambassador Andrew Young on the hand and by the National Security Council on the other - is typical of the turbulence underlying Carter's foreign-policy problems. Another major instance was the Oct. 1 joint U.S. Soviet statement on the Middle East, which triggered angry reactions from American Jews and anti-Soviet hardliners.

In that case, Zbigniew Brzezinski, director of the NSC, has quietly let it be known that he opposed the joint statement. Dr. Marshall D. Shulman, top State Department adviser on Soviet affairs, insisted on it, however, to safeguard the U.S. Soviet connection - despite both Brzezinski and mid-level diplomats at State who feared its political backlash here and the harmful effect of Moscow's reentry into the Middle East.

Those conflicting administration view are dwarfed by the basic lack of agreement at highest administration levels on how to handle Cuba's immense military involvement in Angola - and to a lesser extent in Ethiopia and no fewer than nine other African states.

After doing a slow burn for months from late spring to mid-fall, Jimmy Carter finally exploded in mid-November over Fidel Castro's failure t deliver on "indirect" pledges to the Carter White House that he would rebuce Cuban troops in Angola. The result was press briefings by White House and State Department officials that suddenly raised the estimate of Cuban troops in wartorn Angola to their highest-ever point 19,000 (not counting 4,000 medical and other nonmilitary advisers).

But Ambassador Young believes that neither Brzezinski nor anyone else in the Carter administration knows whether the number of Cuban troops in Angola is going up or down. Young, who virtually took over U.S African policy from the State Department last January, told us Castro has informed American visitors that the United States always underestimated the size of the Cuban military investment in Angola.

"Castro once said that when [former Secretary of State Henry] Kissinger talked of 15,000 Cuban soldiers in Angola, the real figure was closer to 50,000," Young told us in a telephone interview from his U.N. office in Manhattan. "Castro insists he is scaling down his Angola forces."

The difference between Young and the NSC is no mere distinction. It is a contradiction of almost incredible proportions. For if Castro's word to "American visitors" is accurate and he really is reducing his Angolan troops from 50,000, Carter's decision to halt all further moves toward regularizing diplomatic relations with Cuba would look ill-considered indeed.

But in suggesting this defense of castro, Young is out on a lonely limb. On Nov. 18, answering a barrage of questions from reporters surprised at the sudden administration disclosure of 19,000 Cuban troops in Angola, State Department spokesman John Trattner spoke with assurance." I think [we] are pretty sure of those figures and I would say that it would be less than a swing of 2,000 either way" in case of error.

Young has said very little about Cuban troops in Angola since last Jan.25, when he called them a "stabilizing" influence. But Assistant Secretary of state Richard Moose, in charge of African affairs, took a relaxed, almost begin view of Castro' Angolan adventure on Sept. 14. calling it "no burning issue." That was only two months before Carter decided the issue was burning so hotly that Castro had to be publicly spanked.

Moreover, Moose told us on Nov. 25 that a South African military unit had penetrated Angola from Namibia Oct. 27 to fight "a fairly significant action" along the border that might have involved troops of Angola's ruling Marxist regime, headed by Agostinho Neto, as well as Namibian guerrillas. The hint: that South Africa's incursion makes Castro less culpable for his own intervention.

Yet the South African incursion was not mentioned at all when Carter's White House ended its silence and started blowing the trumpet against Castro.

Some critics attribute these disagreements over policy - and over facts on which policy is based - in Jimmy Carter's own lack of ideological commitment. But considering that Young told us he and Brzezinski never had a serious exchange of views on the size of Castro's ideological neutrality can't be entirely blamed.