The premise is,

you buy 100 shares of 0.13sats = 13sats

if you are correct, you are paid 100 shares at 1sat each = 100sats

87sats gain

conversely

you buy 100 shares of 0.87sats = 87sats

if you are correct, you are paid 100 shares

at 1sat each = 100sats

13sats gain