The nameplate rating of the VFD would only be used if the manual does not contain specific information on overcurrent protection and conductor sizing (such as the tables that Aiph5u referenced above). When using the nameplate per NEC 430.122(A) you would be required to size the input conductors and overcurrent protection at 125% of the rated nameplate value. There may be cases where the 125% calculation yields a result of say 40A yet the manual shows a overcurrent protection of 35A or possibly 60A - the manual is the law in that case. I get the point that the spindle likely would never require that much current but the NEC disagrees, their primary objective is to prevent fires and will generally err on the side caution. It is also not a universal answer to just go big on the input overcurrent protection because the VFD components themselves are designed for a specific max input current. You can in theory over size the input conductors if the overcurrent device (circuit breaker or fuse) this would typically be documented in the manual and may be restricted by the lug size on the VFD which may be rated for #4 to #10 wire for example.
I had a case where I was hired to replace a VFD that had an input of 40A with one that had an input of 50A even though the motor it was driving remained the same, I was required to replace 200 feet of wire back to the panel as well.
One of the main challenges with many of the cheap VFD out there is they have little to no documentation, if the do it’s likely not really properly validated/tested/listed (the manual data is probably copied from whatever VFD hardware they attempted to copy while taking out all the expensive components to get the cost down 
)
I’ve tested my 220v 2.2kw spindle using a CT clamp and scope on the input side, with a 5 second ramp time set the highest current draw I observed was 9 amps, with the typical running around 4A (FWIW where I am is somewhat of an outlier, my voltage typically measures between 252 and 258 here, electric co says it’s within their spec and won’t change the tap on the transformer). I wired mine with #10 wire and a 20A circuit breaker which is likely smaller than it should be but I have never had an issue with the setup. I used #10 because it would allow me to go to a 30A circuit breaker if I really had to (ignoring any de-rating of the conductors for continuous use per 210.19)