I got the RPM to read by pushing the Function/Data button twice. KDRusty tried to explain this to me a couple of months ago but he has the 2.2kw spindle with a different VFD control, so I wasn't sure if mine would be the same.
I borrowed a non-contact laser RPM tachometer from a friend just to verify if the numbers I was seeing were accurate, and they are. Since my readout only has 4 spaces, at 18,000 RPM the readout will show 180 and the last space alternates between the 4th number (zero) and what looks like an n.
Hope this helps others who were wondering how to check their RPM, or maybe I was the only one who didn't know this... lol