ta,i wont be running it anywhere near full amps, and yup i spotted that yesterday lol i assumed they were the sameOh dear, you might not like this. Inverter welder I presume?
The way I've found things is that the absolute minimum you need is 50% extra, ideally double. That's for a diesel, petrol would generally need to be bigger yet as they lack the ability to cope with the sudden demand when you go to strike an arc (less flywheel mass).
If you're not using the machine at high amps you might be able to get away with slightly less but really I'd not recommend it, generators and welders don't go together that well and you do need a big generator.
Also be careful not to get mixed up with KW and KVA as they're not the same. I can't remember the exact figures but KVA gives a higher figure which sounds better when selling generators - e.g 6kva is about 5kw, so be careful there.