variance

With absorption costing we calculate the budgeted profit based on the standard profit per unit.
This therefore assumes that the cost of production is based on the standard cost per unit.
The standard cost per unit (with absorption costing) includes the standard fixed overheads per unit.
Therefore when we calculate the budgeted profit per unit, it is assuming that all the costs of production will be as the standard cost card – that the total production cost will include the units produced multiplied by the standard fixed costs per unit.

(If you are still unsure, then watch the Paper F2 lectures on marginal and absorption costing. In those I explain why with absorption costing we end up over or under absorbing fixed overheads, which is the same as the volume variance in the variance lectures.)

Because we are looking at each factor separately.

The total variance is the difference between the standard quantity (for actual production) at standard price, and the actual quantity at actual price.

If the quantity alone was to change, then the effect would be the difference between actual quantity and standard price and actual quantity at standard price.

The rest of the total variance is because the price changed, so we then compare actual quantity at standard price with actual quantity at actual price.

I do suggest that you watch the free lectures on this. The lectures are a complete free course for Paper f2 and cover everything needed to be able to pass the exam well.