Notepad++ the decimal representation of a byte

In Notepad++ in the Extended mode it talks about the \d option which is the “the decimal representation of a byte” which is “made of 3 digits in the 09 range”.
I am still confused about the option. If someone can give me some example of this and how it is used in doing an Extended mode search, I would much appreciate it.

@jamestrowbridge Do you know about ascii codes, like ‘A’ is 41 hex is 65 decimal, and ‘a’ is 0x61 is 97?
Hence, in ext mode, searching for single letter ‘b’ is the same as searching for either \x62 or \d098.