Hexplosive Minefield Question

Hey friends!

Just played my first round of Mechs vs Minions with some friends, it was really fun! I had a quick question about the Ziggs schematics card for Mission 1 though.

The schematics card is Hexplosive Minefield, and is classified as a "one time use" card, in that normally after it is used it is discarded. The card states that you can use it before or after your command line, and that you choose a color of rune tile, and any enemies standing on that rune tile when the card is activated will be destroyed.

BUT

At the bottom of the card, it says "Do not discard Hexplosive Minefield".

This is confusing, because as it is classified as a "one time use" card (based off the symbol of a trash can looking thing at the top, forget the actual name of the type), but then the card itself tells you not to discard it?

With my interpretation, it can go one of two ways, either:

A: You use the card, choose a rune color (we'll say green), and then for the rest of the match enemies spawning or stepping on green runes are destroyed.

B: You can reactivate the card every time it is your turn and choose which color of rune tile to kill enemies on. (In this case I wonder why not just make it a permanent schematic)

We ended up going with option A, since that seemed like the less overpowered option.

Some clarification on this would be great!