Was your 20-30kg something of a guesstimate?
That doesn't look anything like a 60+lb dog ... even 45lb would be pushing it.. only judging by the size comparison with the guitar and a poor picture, obviously..
I've met hundreds of Staffies of all shapes and sizes.. none of the were more than 40lb, very few were even close to it..
That's not to say that there's none out there that are but they are few and far between and would normally be crossed up with something.