Uh, not sure if I am reading it correctly, but is it:

Cantrips + Spells = 19

or

Cantrips + Spells = 15?

For non-Lore Bards at Level 12:

4 Cantrips + 15 Spells (19 total)

For Lore Bards at Level 12:

4 Cantrips + 15 Normal Spells + 2 Additional Magical Secrets Spells (21 total)

And the 15 already includes the 2 spells from level 10 magical secrets.

Good point.

Just to be explicit for newbies: most Magical Secrets spells (levels 10, 14 and 18) count toward your normal total, and are already included in the Bard Level chart in the PHB. Only Additional Magical Secrets actually gives you extra spells; so at level 6, Lore Bards choose a total of 3 new spells, not just one.