Difference between different live load moment values

Good afternoon,

I have attached a screenshot of the analysis of prestressed girder bridge.  I just wanted to know what the difference is between the LL+I: M+, LL+I: M- and LL+I: M. I understand that the first two are the positive and negative moments due to the live load and the impact but I can't figure out what LL+I: M is. Your help is greatly appreciated.