Time displayed in weird way

Hi,

I have attached a sample sheet as easier to see.

Basically the result in n3 displays as 0:00 and the result in n4 as -0:00. Same for o3 and o4.

I have been over and over and over it but can't find any reason at all it should do this?

I want 0:00 to display as 0:00 and anything minus as -0:00

Have set up as [h]:mm;[Red]-[h]:mm and also tried with a 0 on etc. Just not having it.

Any help appreciated. Cheers!