I'm creating a 10th level character which has 5 levels of Arcane Trickster Rogue and 5 levels of Drunken Master Monk. A 5th level ATR will have 3 1st level spell slots while the DMM has no slots.
When multiclassing, does my character keep using the regular Arcane Trickster Spellcasting table on PHB page 98 since the DMM is not a caster, or do I need to use the Multiclass Spellcasting table for a 5th level 1/3 caster only? Does the Multiclass table only matter if you are using levels from multiple casters?