Need help identifying booster pack 4th print variant

So I got some base set packs cheap on Mercari(58 a piece). I opened them and saw it had the light colored variant. I also saw that the top and bottom of the flap on the back was tightly crimped. I read this is a sign of tampering. I checked the copyright and its 1999-2000, like the UK 4TH print. The color and trademark symbol lines up great when compared online with the packs. HERE IS THE CRAZY PART.

I decided to weigh them and normally heavy is 21-21.3. All od these packs weigh 21.9!!!!!!

Makes no sense! Maybe extra glue from tampering? Did 4th print weigh more?

Thanks so much for taking a look, ill post pics if I have to but the artwork and pack is self explanatory.

Actually pictures would be useful here.