NM calculations are off

[Franz Ferdinand]

I was testing Sealion campaign and in three turns I have captured London. NM calculations are off, as you can see in the photo. Even if London was supposed to be 50 instead of 150 NM (and it clearly says it is 150 in objective tab), it is still of by 1. Also, how come that GB can continue fighting (I played for two more turns), even though their NM is 0? [ATTACH]36271[/ATTACH]