Subtraction of unsigned negative values still works just fine because of two’s compliment. (uint8)(-3) is 253, for example, and (uint8)5-(uint8)253 = (uint8)8,

Subtraction of unsigned negative values still works just fine because of two’s compliment. (uint8)(-3) is 253, for example, and (uint8)5-(uint8)253 = (uint8)8, corresponding to 5 - (-3)