X64 USETUP shows wrong size while creating partition

When you create a partition in x64 usetup, it tells you to enter the size in MB.

However, the max size is wrong(9 instead of 20472).

If you type 9, then it will create a full-size 20472MB partition, but if you type 8 or less, it will create as you typed.

If you type anything larger than 9 it will turn it into 9 when you press enter.

The x86 version doesn't behave like this, it shows 20472, and I uploaded a screenshot.

In the log, I created "9MB" and 8MB partitions in x64 version, and created real 9MB partition in x86 version.