Is this a bug in excel ????

Please try this :

Key any number in any cell (let say I put no 1).

then change the format to percentage.

Keep the cursor in that position, now hit backspace then key any number
1, 2,3,100, etc, as you can see the result will be multiply by 100,
meaning : before it was 1% and after backspace it became 100%, please
explain. Heaps of thanks !!!