Update integers-and-floating-point-numbers.md (#42755)

* Update integers-and-floating-point-numbers.md

This sentence also confuses me. 
Copied  from [StefanKarpinski](https://discourse.julialang.org/t/i-can-not-understand-the-meaning-of-this-sentence-on-the-doc/21010)

* Update integers-and-floating-point-numbers.md

* fix whitespace

Co-authored-by: Viral B. Shah <[email protected]>

Author: likanzhan

doc/src/manual/integers-and-floating-point-numbers.md

@@ -173,8 +173,18 @@ UInt128
 As for hexadecimal literals, binary and octal literals produce unsigned integer types. The size
 of the binary data item is the minimal needed size, if the leading digit of the literal is not
 `0`. In the case of leading zeros, the size is determined by the minimal needed size for a
-literal, which has the same length but leading digit `1`. That allows the user to control
-the size.
+literal, which has the same length but leading digit `1`. It means that:
+
+- `0x1` and `0x12` are `UInt8` literals,
+- `0x123` and `0x1234` are `UInt16` literals,
+- `0x12345` and `0x12345678` are `UInt32` literals,
+- `0x123456789` and `0x1234567890adcdef` are `UInt64` literals, etc.
+
+Even if there are leading zero digits which don’t contribute to the value, they count for
+determining storage size of a literal. So `0x01` is a `UInt8` while `0x0001` is a `UInt16`.
+
+That allows the user to control the size.
+
 Values which cannot be stored in `UInt128` cannot be written as such literals.
 
 Binary, octal, and hexadecimal literals may be signed by a `-` immediately preceding the