How do I determine the proper bonuses for my attack and damage rolls? [closed]

I am a half orc monk at level 14. I am using a homebrew gun called the demon of powder, which has 6 charges that it expends instead of regular bullets as ammo. My stats are 14 20 14 8 15 10 in order. in the description of the weapon it says i get +5 to both hit and damage rolls, but on dndbeyond it says i have +6 to hit and 2d8+6 for damage. My DM said that the regular damage for this is 2d8. I’m very confused where dndbeyond is getting the 6s from. Additionally, should i manually add in the +5 to hit from the description or is it already included?