First of all this is one of the best question.

Let us do our analysis in decimal system -

Let we us have 1-Digit Mantissa and 2-Digit Exponent then Mantissa range $-9$ to $9$, and 2-Digit Exponent range $0$ to $100$.

Now possible numbers are $-900, -800 ...... -1, 0, 1, 2 ....10, 20, 30,...800, 900 $

It could be observed clearly that max difference between two consecutive number will be max(100) when exponent value is max. Similarly min difference between two consecutive number will be minimum(1) when exponent value is least.

Same principle could be used in the mentioned question.

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