If you have a level 1 spell that does 2d6 damage, and 2d6 more for each slot level above 2nd, you can check "Higher Lvl Query". Then, in Higher level dmg dice you put the number of dice that you need to add for each level (here 2), and in Higher level dmg die you put the die that you need to roll (here d6). Output simply show the level used in the subheader (says something like Level 1 (as 2) if you launch it at 2nd level).