Orange peak/off peak tarriff

I've managed to negiotate a custom tarriff with Orange where I get 1000mins
xnet offpeak and 200 mins xnet peak. I've enquired and been assurred that
all peak mins will come out of my peak allowance and vice versa but remember
someone mentioning that it doesn't quite work like that.

I'm just worried that if I stay within these limits, the order in which I
use the minutes may effect the outcome. Can someone shed some more light or
is this not a problem anymore?

Thanks