It doesn't matter if it was a G day or L day, that's why I used only 15 average duty days per month, hence another 15 G ,L and U days each month. It is a conservative number I think. But feel free to use only 10 duty days per month, then your case would represent 0.003 %.
The point is that we do not know how many of those extra days are being used, and therefore what impact CC would have.
It's only about math (=money). What else???