What are the three modifiers on a Thieves Tools roll?

Hi, In my game, a rogue made a Thieves Tools roll that's displayed with these modifiers: Thieves' Tools  (4+0+4) Why are there three of them? One of the 4s comes from the Dex modifier, the other comes form the expertise, but why is there 0 as the third modifier? Thanks!

It depends on the sheet/macro called to use them, but on the Roll20 5e OGL sheet there are three mods available (Ability, Proficiency, and Mod) where mod is any custom amount applied. Typically when rolling from the sheet it adds them all up before sending and appears as something like "1d20 + 8[Mods]" so if it happens to be using something custom it could show up differently. If your sheet is different or the roll is different we may be able to help adjust the output to be more clear.

Thank you, I'll talk to the player. It would be nice if the hover text explained where each modifier came from.

You can have it do that by adding tags, checking the sheet should tell you (assuming you have access to it). If you can determine what they clicked we can help explain a bit better.