Formula for standard cost variance.

Hi

Here i have a production order variance as below:

OVH3 is a surcharge based on the M1 group, OVH3 = M1 * 0.03.

Now base on the output of this dialog, i found quantity variance 0.48 = (7.5 + 8.5 ) * 0.03

I don't understand why the overhead quantity variance is based on the material M1 "Price Variance" and "Quantity variance".

anyone who knows the formula for how to get the variances ?

Many thanks.