Hello Scott,

I have a question about the Computer Error promo card.  Do you decide how
many cards you draw before you start drawing, or can you decide to stop
drawing as you pick up cards?

Thanks in advance.

Sincerely,
Christopher Lee

[Trainer
Computer Error (Rocket's Secret Machine)

You may draw up to 5 cards, then your opponent may draw up to 5 cards.
Your turn is over now (you don't get to attack).]

As also with a mulligan, you must decide the number of cards you will draw from it BEFORE you start drawing them.  Once you being drawing cards without stating the number, you are presumed to be drawing the maximum allowed.

Scott