Can't work Javascript auto-bookmarklet for random number input between specific ranges

I am trying to create javascript bookmarklet that it can fill boxes with numbers, range between 55-99 on any random web site. I wrote this but it doesn't work. Please help me ASAP.

var min = 55;
var max = 99;

Math.floor(Math.random() * (max - min + 1)) + min;,

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