No. The email I got says very clearly "$25.00 credit can be used only for purchases with a combined cost of $25.00 or less."
There's no way to combine remaining balances of the $25 with anything else, so you'll almost certainly end up with something under $1 remaining when you're done spending it.
The key is, if you want to make any larger purchases with it, make those first. Then you can blow the last few bucks on a few 99 cent apps or something and be left with less than a buck "wasted".
If I was worried about a 75 cent balance on a freebie that came with my Nexus, I wouldn't be the kind of person to piss away $250 on the thing to start with. It's a toy, and I will use the freebie that came with it to buy virtual toys to use on my toy.