With some of those two, they writing the sums they were bought for, like Romagnoli, Gagliardini, Caldara and some others.
Rest they just estimating roughly on hype/predicted bids etc.
Rugani was bought for 3m fully, and 1.5m half share before that. No way they think a 21 year old azzurri player playing for Juve is worth 3m lol.