Hi,
I use Delta VFD's (Taiwanese brand made in China) and have always had good results. I do not like nor do I trust el-cheapo Chinese made VFD's.

This is from the MS300 manual (of my new VFD)

Note how there is a table that describes the voltage applied at a given frequency.
There are up to four points (a frequency and a voltage pair) for each of the four possible motors. That this drive can have up to four different motors complicates things a little.....but in your case all
you need worry about is the V/F table for your one spindle. The end point is the voltage at max frequency, I would guess your motor voltage, say 220VAC at 400Hz.
Then you may program several mid points....for example 50Hz and 27.5VAC.

It is a good idea to program a minimum frequency, usually 1/3 of max frequency, 400/3= 133Hz. This will ensure that you don't run your spindle too slow and blow it up.

With a beginning (or midpoint) and and endpoint the drive will now know what voltage to apply at any given frequency.

God knows what terminology YL use but there will be some parameters that mean the same thing. Good luck.

Craig