Capped artifacts are not shown in this optimiser, and the cost to upgrade them is ignored. The discovery cost for them is taken into account. What this means is that the levels shown might not be affordable if your relic total is very low (low enough that you can't easily max out all capped artifacts. To fix this problem, temporarily lower 'Non-BoS relics spent%' to some value where you can afford the suggested upgrades, until you can easily max out all the capped artifacts.
When using this artifact optimiser, you will see a list of artifacts with levels next to them. These are the levels at which your artifacts would be optimal. Try to match the levels for your artifacts with the suggested levels somewhat closely. If it doesn't match exactly, that's not a problem. If you have overleveled one or more artifacts, just try to follow the general direction of the suggestions, and avoid leveling the overleveled artifacts. In a couple of prestiges' time, they will no longer be overleveled, and you can use the artifact optimiser normally again.
If you have any question regarding maths, you can join Mmlh's support server. For anything else, join the Tap Titans 2 Compendium support server.
Lifetime Relics: Enter your Lifetime Relics from the stats page here.
Artifacs Discovered: Enter the number of artifacts you discover.

Artifacs Salvaged: Enter the number of artifacts you salvage.
Enchantments Owned: Enter the number of enchantments you own.
Build type: Select your build type.
Last hero: Enter main hero (higher damage hero).
Ascension: Enter your main hero ascension (You can see the acension on hero border) yellow Ascension 3, green Ascension 2, blue Ascention 1, grey no Ascension.
Split: Split or not your damage source. "Ground" splits your damage source between all ground heroes (Melee, Ranged, Spell), same for "Flying". "All" split your damage across all hero type.
Gold Source: Enter your main gold type.
% of Relics to BoS or BoS level: Enter your actual BoS Level or switch to % of Relics to BoS.
% of available relics used : Percentage of available relics. Note: This is to counter rounding errors as well.
Durendal Push: Select if you want to durendal push.
Letter Notation: Select to output Letter notation.
Rounding: Select the number of digits for the results.
Percentage: If you press Percentage the artifacts will be sorted based on percentage.
Include: Select all your available artifacts.

If you want to be able to switch between Abyssal and The Main Game value, please

and you will be able to use this feature.