Is this a glitch? ETH TPS down to 6.35?

Source: https://blockchair.com/ethereum/charts/transactions-per-second

I checked it out today and I saw a MASSIVE drop in TPS from 15 on 4 June to 6.35 today (7 June). Is this for real or is it just a glitch / delay in the data? Or maybe the source is not reliable?

What do you guys think?