In the size put 100 instead of 450?
Yes, but you must add the % symbol.
If you put just a number in, the browser will treat it as a pixel value and a pixel value is an absolute value, whereas a percentage value is a relative value. So wherever you post that picture with a value of 450 pixels, it will be that size, even if it is too big for where you are putting it.
Imagine a pint of water for example. One pint is an absolute quantity. Tip that into a bucket an it'll fit just fine, tip it into a coffee cup and it'll overflow.
But fill a bucket 100% with water and it fits, fill a coffee cup 100% with water and that fits too.