The smallest denomination is called a "grugget" 😂

Yes, mana is displayed as whole numbers but calculation relating to mana treats them as a decimal. For example, my displayed balance is currently 28,231 mana but the value stored by Manifold is:

You can see this under notifications --> mana in relation to your loans.

yes but they dont display - there are lots of weird rounding errors where you're supposed to get 1 mana and get 0 mana instead, or visa versa