Simple 5e D&D Question on NPC/Monster Form

So... for attacks:  Sometimes there's just a number in the melee to hit.  For example, with the Kobold's dagger attack I'm looking at 2.  So I think that means if I click Spear Roll20 will generate a number 1d20+2.  If I want a number 1d20+5, do I overwrite 2 with +3 or +5 or simply 5?  In other words, is the + additive to a base stat modifier or is it a simple overwrite and the positive is assumed? Would this be the same for all such calculations?

You'd overwrite it with 5. Unlike a PC sheet, the NPC ones don't grab values from other places on the sheet, each entry on the sheet is self-contained.