Magical Secrets Cantrips

When selecting a cantrip using Magical Secrets, the cantrip is counted towards your limit of cantrips known. 

So if I'm a level 6 Lore Bard who knows vicious mockery, minor illusion, and message, selecting booming blade as a magical secret will display a warning that I know 4/3 cantrips, and that I should unselect one. 

 If I understand correctly, this shouldn't be the case.

Unfortunately, you do not understand correctly. Spells learned through Magical Secrets 100% count against your number of spells known, including Cantrips.

It says they are included in the spells known column, but cantrips known are in a different column. 

Quote from Asmo___deus >>

It says they are included in the spells known column, but cantrips known are in a different column. 

 That’s because WotC sucks at wording. They should have written “The chosen spells count as bard spells for you and are included in the number in the Spells Known and Cantrips Known columns of the Bard table.”

The entire reason that the Bard gets 2 new “Spells Known” (from 12-14) and 1 new “Cantrip Known” (from 3-4) all at the same level as Magical Secrets is to accommodate for the player’s choices.