Variable overhead variance

Sir I just read through the study text
And there was this one specific thing about variable overhead vaeiances

It said that variable overhead variances are usually valued at direct labour input
But sometimes there could be an instance where it gives units
And for these instances we have to value the total variable overhead and we can’t find the expenditure and efficiency variances

Sir i was wondering how do we find the total variable overhead variance when they give it in units instead of hours

Do we use budgeted units in calculating the variance(I’m assuming we use budgeted units because I remember that in direct material variances we used budgeted units when to find the total variance when they didnt give kg quantity)