How Many? Activity Cards Level I build perceptual subitizing skills with simple dot patterns. The Level I deck of cards presents simple dot patterns to practice subitizing number up to 20. These card decks are great for small group practice or independent exercise as self-checking number words and numerals provide the answer on the reverse side of the card. This How Many? set of large 5" x 5" cards contain 50 two-sided activity cards.