That's just the default diplomacy penalty ("First impressions"; "They just plain don't like you.") per difficulty. The player gets a random diplomacy penalty at the start of the game that scales by difficulty. This mod doesn't make any changes to diplomacy, but since Pro is one difficulty higher than Deity, the diplomacy penalty is also one difficulty higher.

Oh I see, thank you for explaining. I was going through the files trying to find it, hah. No problem, just another challenge.