Str bonus not being applied properly?

[Heresy69]

My chr has a 17 base str and when I look at a weapon it says that I get +3 to both to hit and damage due to my str mod. However I have a necklace equipped that gives me a +1 to str making it an 18 which would be a +4 mod. Yet when I look at any weapon now it is telling me that I have a +4 str mod to hit and a +3 str mod to damage still. I am at a loss as to why this is happening. Do I need a 19 STR to be able to get the +4 to both attack and damage for some odd reason?

[Visty]

the decriptions of weapons only count your base str without items

to see the real numbers check the detail box in your inventory