Hi, I have a problem, the mod displays me negative durability instead of the actual durability of the armor or items

Yes. That's what the "Percent to show damage" option is for. Set it to 100% to always show remaining durability, 0% to always shows what's missing to full repair. Default is 80%, so for netherite items that have approx. 2000 total, it'll go from 0 to -400 first, then from 1600 to 0.

Thanks sorry for that x)