What is the format used to store an integer in two bytes?

Question

css

There are two bytes, for example:
0x20 and 0x0A the output should be 0x100
or
0x20 and 0xFF the output should be 0x107 (or 0x110 I can’t get a more accurate value)

The first byte, as I understand it, is simply dividing the value by 8.
How to get the second one?

Answer 1

The owner is a gentleman, give him a value of 999 and he will be above all the elements.
Only z-index is not needed here. And the correct positioning inside the form. The calendar should not leave its limits, as it seems to me.

Answer 2

give a link to the page where this calendar is better