Number of desktops

Hi - currently I have 16 desktops arranged like below. Note that it says I have 16 and need 4 more - however clicking “Add Desktops” doesn’t do anything. Is TotalSpaces2 coded such that 16 is the max?

There should be a friendly error message at this point - OSX does not allow more than 16 conventional desktops on a single screen.