It also contains a typo, it should be "the number of permanent cards")
Is that even right? I think "permanent" can only refer to actual permanents. You'd have to specify "creature, enchantment, land, artifact and planeswalker cards" since "cards that aren't instants or sorceries" isn't a thing. This has slightly bothered me for a long time, because I teach a lot of people magic and one of the first things I do is explain the different kinds of cards, and showing them this vs. that is easiest for a lot of people.
Land vs. Spell (to show everything that isn't a land is technically a spell)
Permanent spell vs. Non-permanent spell (to show instants and sorceries being "one-shots," people who aren't familiar with the concept of magic / fantasy need this badly)
Creature vs. non-creature, then break it down to the more specialized types.
So while it's a pretty important part of the game, and most people who have played other card games or are familiar with fantasy stuff in general can grasp the difference between summoning an artifact to wield and shooting a fireball at your opponent, someone who has managed avoid the phrase "dungeons and dragons" their entire life gets real confused real easily.