Critical Path and Negative Float

I am having a problem with Suretrak calculating the negative float. My longest path does not have the same negative float. When the activity spans a period where there are more holidays (Christmas etc) rather than just weekends, the negative float takes holidays into account, which I believe should not be the case. A continuouse path should have the same negative float.

Is there any setting in Suretrak which makes this result. This schedule has the same result on all the laptops within my company, however, when I ran this on my friends laptop (different copy of Suretrak), the results were not the same!

Any clues? Need Help, please.