If you want to cover your planck in blanks, and you've got a grid planck, you'll need to buy the 108-key set of blanks since the 87-key doesn't have enough of the same row profile to cover the bottom row of the planck. (Learn from my mistake)
poinckYou should be fine. There are exactly eleven 1U keys in the row above the spacebar. This includes the arrow cluster. If you were going for the full grid on a Planck, you'd need to order the 108-key set since that adds a further three 1U keys.