I see your point, but...
you wouldn't say "320 Credit" as it would then garner the plural form of the word, hence "320 Credits." Much the same as BitCoin is the singular form, until you have multiple, whereas they become "BitCoins."
An American Dollar is much the same, where it only becomes the plural form when you have more than one. "I have 1 dollar." versus "I have four hundred dollars."
STT,
Thanks for the insight and constructive criticism!
What I mean is that just because something is named "credits" does not mean that the one who uses it will feel compelled in any way to say "1 credits". They will simply call it "1 credit" intuitively.