Final tabulation of yesterday's votes will take as long as a week because of the elaborate process required by the Proportional Representation system of voting that the city uses.

Voters yesterday ranked in order their nine choices for council seats. Under the system, if any of the 25 candidates receives 10 per cent plus one of the first-choice votes, he is elected.

The excess votes of winners and the first-choice votes recorded for the lowest candidates are then redistributed to each voter's next choice. The process continues until nine candidates make it over the quota and are elected.

Beginning this morning the election commission will tabulate the votes for city council, holding off on Cambridge School Committee ballots until Saturday.

If the convention does take a fifth council seat, it will be result of the group's strategy rather than any real shift in the thinking of Cambridge voters.

Throughout the campaign, the conservative Independent councilors have maintained that there were no real issues this year and confidently predicted victory, relying on the solid working class constituencies they have built up over that last few years.

"We got our vote out," Sullivan said, "and that is the important thing."

With an extensive publicity campaign, however, the convention told Cambridge residents that an Independent victory would mean the end of rent control and the firing of the city's liberal city manager.

Publicly, the Independents have all but igonored Cambridge Convention '75, but about a half hour before the polls closed yesterday, Sullivan acknowledged that the group "had certainly done its homework.