If you click on the "instructions for this section" of the personal statement section, you will see they specify it has to be 4500 characters including spaces. When you paste it in, you can see how many characters, but be careful when you paste from Word to AADSAS, because for me, for some reason, they word count was different.
It is 4500 characters. I didn't have any issues on the count when pasting it from Word to the AADSAS form. Be sure to limit the number of tabs or enters, if any.