The 20/10 roster is another thing actually, let me make the same example, in Ethiopia you join directly with 20 work days 10 off days, accrued leave has nothing to do, in the 20/10 there’s no leave anyways.
If you divide 30/12 is 2.5 days, the rest is 7.5.
It’s a strange 20/10 then, not attractive at all and you still lose the best flight.... We’ll see the result.