The article says they used volunteers and AI to count the number of people who voted from video feeds:
after counting votes and comparing them with the official turnout, the software found discrepancies in 11 regions so huge that it made it impossible for the election result to have been accurate
based on volunteer analysis of video footage from 233 polling stations in 17 regions revealed a discrepancy in turnout equivalent to 81,731 voters. Based on election statistics, analyst Sergey Shpilkin estimated that 10 million additional votes had found their way into ballot boxes nationwide.
So they have strong evidence for around 10 million forged votes, but not which party they were cast for. Then again, when you consider that all political parties except Putin's come in below 10 million votes, the selection of who might have benefited from it becomes rather small :)