10.1.4  Difference between the representation of (3.1-3) and of 0.1

For the representation of 0.1:

hence α=1 and

therefore the representation of 0.1 is

the last octet is 1010, indeed the 2 last bits 01 became 10 because the following digit is 1 (upper rounding).

For the representation of a:=3.1−3:
Computing a is done by adjusting exponents (here nothing to do), then subtracting the mantissa and adjusting the exponent of the result to have a normalized float. The exponent is α=−4 (that corresponds at 2·2⁻⁵) and the bits corresponding to the mantissa begin at 1/2=2·2⁻⁶: the bits of the mantissa are shifted to the left 5 positions and you get:

Therefore, a>0.1 and a−0.1=1/2⁵⁰+1/2⁵¹ (since 100000-11010=110).

Remark:
This is the reason why:
Input:

returns 9 and not 10 when Digits:=14.