$20 for a $20 off $40 code. So, you spend $120, you pay $60 if you buy his certs. It was likely a Google Offer thing. So it's a good deal if you're spending $$$ at NewEgg now.
But he says "$20 for each". I assume that means per voucher. So if you bought all 3 for $60 then bought something for NewEgg for $120, you get that for $60. Plus the $60 you bought the codes for makes it the same cost.
Unless it's $20 off every $40 you spend, in that case it's different.