Relationship modifing issues

I manually set the relationship score to around 80 to 100 for Erosia & Velion. But then when Franz updates their relationship by adding or subtracting, it starts it over from 0. I then tried to get Franz to add the points I need it to be at but if I asked for 80, it would do 40. If I asked for 40, it would do 20. But also each time, it would add it from 0 points.