88v would be well in the territory of a brownout, but according to that graph you are sitting comfortably within 10% of 115v, with one exception. This isn’t bad, if you viewed the graph with the y axis range set from 0v-140v it would look nearly flat. I wouldn’t worry about it, the UPS will handle the small transient stuff.

The silicon die could easily chip a tooth as well, the stuff is insanely hard.