I believe that the entire point of presenting the roll this way was to simplify it for the player and make it more intuitive. Judging by the number of times this confusion has come up though, it's safe to say that did not work.
Larian should offer the option to display the dice rolls in an advanced style, showing two dice when there is Advantage or Disadvantage, showing a d4 if Guidance is active, and showing the actual DC, and adding the modifier after the roll. (Then allowing Bardic Inspiration to be spent, if applicable.)
Or at the very least make it crystal clear in the log. But I would prefer it to be more clear in both. When you hover over dialog options, it does a good job of showing you what SOME of the bonuses are...the next screen that shows what you need to roll should explain how it got to that DC.
