The decreases, like the increases, are supposed to have the same tension on either side, the mirrored decreases are supposed to look as similar as possible to each other.
Some of these swatches required writing instructions for the technique.
Swatch 7: SSK & K2tog
Swatch 8: K2tog & SSK
Swatch 9: SKP & KSP
Swatch 10: SSP & P2tog