I think they mean that Steam filtered out the Chinese internet-café responses from their hardware survey results as they were skewing the figures - single machines were being reported multiple times as different gamers signed in on them.

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From the linked page:

>Around August 2017, we started seeing larger-than-usual movement in certain stats, notably an increase in Windows 7 usage, an increase in quad-core CPU usage, as well as changes in CPU and GPU market share. This period also saw a large increase in the use of Simplified Chinese. All of these coincided with an increase in Steam usage in cyber cafes in Asia, whose customers were being over counted in the survey.

>It took us some time to root-cause the problem and deploy a fix, but we are confident that, as of April 2018, the Steam Hardware Survey is no longer over counting users.

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Since they fixed that, English has gone back to being the most common language with 40% of users, Chinese second with 25% and Russian third with about 10%. Should be noted that English is probably over-represented as a lot of Europeans use English.