Hi LoGo,
The way I have always been taught is that leave days DO count as days off, as do sick days, because they are days free from duty. I have worked for 3 charter airlines and none of them would allocate extra days off if a crew member had already had leave days.
With regards to the average 8 days off....It only has to 'average' 8 days off and the actual minimum is 7 (see point C). You can therefore have 9 in the first four weeks, 7 in the second and 8 in the third etc etc. This is calculated on a rolling basis so each three period block must contain an average of 8 days off per period.
Hope this helps
BTS