二十

二 = 一 : Mnemonic symbol: a capacitor, because the two strokes remind me of the symbol in electrical drawings. Albert Einstein (Ø) is experimenting with a capacitor (二) in the space station's bathroom (Ø4). He finds that it's uncomfortable to discharge a capacitor using two flutes (一).

十 = 一 + 丨 : Mnemonic symbol: a holy cross. Sherlock Holmes (sh-) is investigating a very strange thing he found in the kitchen of the space station (-2): A big pyramid made of ten (十) crosses (十), which are in turn made out of flutes (一) and dinosaur bones (丨).