Spelling mistake on H1B extension approval

[query2]

We got an approved H1B extension approved - but it has a spelling mistake in my last name: instead of
XYZABC it is XYZACB - will it matter when I go for stamping ( I am going to Toronto) ?

My attorney said it should not make any difference. I wanted to get it changed - but I learnt that it takes 3 months and I have to go for stamping before that...

Any experiences: good or bad ?

Thanks,