vC = Computed MAG VAR?

[Nazgul 1-2 -Kjell-]

What is the difference between vC = Computed MAG VAR and MAG VAR = Magnetic Variation And how do I find out what value vC it has. Because Jester seems to know, but I don't know. / How do I have to enter this?

Spoiler

Edited December 29, 2021 by Nazgul 1-2 -Kjell-

[Naquaii]

VC is WCS calculated magnetic variation using the INS and compass. VM is the manually entered value that a RIO or Jester can enter, that's what the kneeboard value is for.

These two do not always correspond as external factors can affect the calculated magvar, like a carriers magnetic signature as an example.