Each digit is multiplied by 16 raised to the power of the digits place (starting with zero), then all of the results are added together.

&H2E35 = 11,829

(5 * 16^0) = 5 * 1 = 5
(3 * 16^1) = 3 * 16 = 48
(14 * 16^2) = 14 * (16 * 16) = 3584
(2 * 16^3) = 2 * (16 * 16 * 16) = 8192
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Total = 11829