You can see this collector number on the bottom of each card, usually followed by a slash and the total number of cards in the set, excluding secret rares
Mostly do breaks
Remembering it is part of how to play Yu-Gi-Oh

Product Specifications: *The card booster boxes shown are examples only and are not included with this product. Name: Semi-Hard Holder for Trading Card Game (Pokmon Card) Booster Box Collections. Sizes: Regular Size Internal Dimensions 5.5 x 5.7 x 1.6 inches (139 x 144 x 40 mm) (designed to accommodate a box that is in shrink wrap), Half Size 5.5 x 3.0 x 1.9 inches (139 x 75 x 48 mm) (designed to accommodate a box that is in shrink wrap). Thickness: 0.01 inches (0.3 mm). Material: PET plastic. Color: Clear (transparent). You can choose from sets of 10 or 5 of each size or a set containing 5 of both the Regular and Half sizes. Amazing Value for Money: Many collectors feel that while storing multiple collectibles in acrylic or similar hard cases is too expensive, quality becomes a concern when the cases are too cheap. With the aim of delighting those collectors, we have developed storage cases that deliver both high quality and amazing value for money by increasing production quantities and reducing logistics and intermediate costs.These cases are strong enough to enable stackable storage, have a high degree of transparency, and feature a protective film to prevent damage prior to use, UV protection, and a safety lock mechanism. An instruction manual (English language not guaranteed) is included

You can also banish any HERO from your graveyard to add Polymerization from your deck to your hand
Finally, place a filler card in a deck sleeve, then slide your printed out proxy over top of the filler card