For instance, if you're a sorc 12 / bard 6, and you get the College of Lore's Additional Magical Secrets feature:

At 6th level, you learn two spells of your choice from any class. A spell you choose must be of a level you can cast, as shown on the Bard table, or a cantrip. The chosen spells count as bard spells for you but don’t count against the number of bard spells you know.

Is the level of spell you can select based on your spell slots (which at 18th level are high), or solely on the bard table of known spells (which would mean 3rd level)?