How does attack work?

Sorry, another dumb question but I don't have a lot of time before our next game session... I'm looking at a Character Sheet for one of my players, and they have a number of weapons listed. If I click on one of the weapons, some rolls appear in the chat window. Why do 2 rolls appear for a single weapon? Our Dwarf fighter has a one-handed battleaxe. Listed under her stats is "ATK 4". I *thought* her attack roll would be: The Natural Dice Roll + Strength Modifier (+2) + Proficiency Bonus (+2) + weapon ATK bonus (+4). But that seems overpowered. Now I think that the roll is: Dice + Str Bonus + Proficiency Bonus, which is a total bonus of +4 which is what's reflected in the weapon's stats. Is that correct? Thanks.

You might want to post which character sheet you are using for which game system. 

Sounds like 5e. Attack roll should be 1d20 + Str mod(2) + prof bonus(2) = 1d20 +4.  You might be seeing two attack rolls if the sheet is set up to always roll advantage. I'm playing the odds and guessing you are using the 5E by Roll20 sheet. You can click the cog wheel and change to the desired roll type.

Thanks, yes it was 5e. I appreciate the pointers!