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It's 'current_supply' which increased less than usual, right?

Yes, "current_supply".
June 19 07:40 UTC - 250,655,290
June 20 07:00 UTC - 250,697,528
June 20, Hard Fork 19 at 15:00 UTC.
June 21 07:00 UTC - 250,723,099
June 22 07:00 UTC - 250,738,816
Now 13:30 UTC - 250,745,349

I ran through the transfers to @null. There were no Steem transfers, only SBD, so it's not that. I'm pretty sure transfering to @null is the only way to burn Steem.