When doing arrayPolar (apart from being a really fiddly and annoying tool), you cannot enter a negative value for the Z offset.
There is also insonsistency around terminology. When defining the angular fill you have to define the total angle (unless you specifically choose step). When defining the Z offset, it defaults to the step offset rather than the total.
These two are exactly the opposite of what I’d normally want. Either way, I think these options would be far better dealt with via a pop up dialogue that allows you to amend all settings and preview the results. I find myself having to try it, realise I chose something wrong, redo it. Over and over again.
BUT, that the Z step doesn’t allow a negative number is a pretty basic issue.