AS IF FOLLOWING the fortunes of Metro didn't already tax the mind almost as much as the billfold, there were reports from Annapolis this week about a " $25-million misunderstanding" - specifically, about what Gov. Harry R. Hughes may or may not have said to suburban lawmakers about providing money for the transit system. The hazy impression left by certain legislators' accounts was that the governor had backed off from a promise to transfer $25 million to Metro from state funds. Did he? And if he did, will this kill Metro?

No and no. Even if Gov. Hughes had wanted to transfer the money directly, he couldn't have done so without some some kind of eventual legislative approval - and therein lies the political hang-up: The legislature this year is not sympathetic to Metro's plight, and hardly anyone in Annapolis relishes a nasty battle if the system can make it for another year. Besides, Gov. Hughes already has offered an extra, one-time-only grant to help pay the Maryland suburbs' share of Metro's annual projected operating costs for its bus and rail system - thus allowing time to study various approaches to some permanent, reliable financial formula.

The $25 million was being sought for construction of the subway - money that definitely will be needed even if it is not immediately crucial.What Gov. Hughes first said about this amount was that he would support legislation to finance this amount - which is far different from simply transferring the money by administrative action. That, apparently, was the point on which the misunderstanding arose; so now the suburban lawmakers are acknowledging that they may have read too much into their meeting with the governor and, what the heck, wait 'till next year.

That's the reality of it, anyway. So long as Gov. Hughes remains sympathetic to the financial troubles of Metro, the system can get by for a year with the money to help pay the suburbs' share of operating costs. But he and those legislators who understand the situation have their work cut out for them next year. Both the Carter administration and Congress have made it abundantly clear that the governments of this region must come up with tax commitments to cover operating costs if federal assistance is to continue. That is why in Annapolis, Richmond and the District, the time for any more "studying" is rapidly running out. Next year, the legislatures of both states will have to move or Metro - and the people of the region who do or will use it - will be in serious trouble.