A recount in Wisconsin’s two largest counties (by population) ended with Biden gaining a net of 87 votes over Trump. Together, the two counties make up 26% of the state’s population. Biden’s statewide margin of victory is about 20,600 votes.
After the 2016 election, a full recount of the votes cast in the state (requested by Jill Stein’s campaign) netted Trump 131 votes. He beat Hillary Clinton by 22,748 votes in Wisconsin.
A total of 1,543 votes were added to the overall tally in the 2016 recount, and only 245 (net) in the 2020 recount.
The system seems to work pretty well after all, at least in that state. Back in 2016, Trump’s campaign sued – without success – to stop the recount. It’s almost a reflex with them: stop counting while we’re in the lead.