I would not be surprised if at their largest they might have taped 22.
you have to remember a few things:
1. he was a legit 6'6/6'7 and weighed 330 at his heaviest according to his book. This is a lot bigger than almost any pro.
keep in mind that this is not a muscular arm, like a pro in contest shape, so the fat around it will increase the measurement.
but I doubt they were 24 inches.
ronnie in 2003 arms looked way way bigger than Hulks ever did and I doubt even they were 24 inches on stage:

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sorry hulk