Can someone give me some insight into how the VR and MS settings work in conjunction with the Bit/Tool settings?

I am spec'ing feeds and speeds in Aspire and also trying to fine tune the SPB VR and MS inputs.

I'm fine tuning as I'm cutting some extreme detail (.0312 and .0156) over large surfaces (17" x 17") and am working to dial in the extremely fine detail but reduce my machine times.

Thanks for the help.