12v --> 10v Nowforever D100S2R2B inverter & MKS-V-V02 CDXHCTECH board

[CarecaIII]

Hello. I bought a cnc 6040, 2.2KW on aliexpress from Chinacnczone.
The cnc works well enough only that I have a problem.
The spindle speed is about 20% greater than the one set as shown in the following graph:
s1000 -> 23.60
s2000 -> 40
s4000 -> 74
s6000 -> 114
s8000 -> 150.80
S10000 -> 187.60
S12000 -> 230.80
S14000 -> 270
S15000 -> 290
S16000 -> 309.6-310
S18000 -> 356
S20000 -> 400



It should go to 400Hz when I set s24000 and not with s20000.
I opened the controller and found that they connected the output of the inverter (Nowforever D100S2R2B) that is 12v to a board input (MKS-V-V02 www.cdxhctech.com) that instead expects10v, as shown in the following scheme.



How can I solve the problem? Where to get 10v?

Thank you.