Arduino RFID and OEM 125kHz USB Proximity RFID Reader

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Hello. I'm doing a project with mySQL database and I would like to know what information RFID reader read.
Using Arduino UNO and RC522 RFID Module, I print the UID Tags number in HEX while using the RFID Reader, I'm not sure if they're printing the serial number or others.

I thought it was the same but when I scan its two different number. One is UID tag number and the other one I'm not sure.

For example;
Scanning using Arduino and RC522 in HEX
UID tag number; 20 63 CA A3
Scanning using Arduino and RC522 in DEC
UID tag number; 32 99 202 163
Scanning using OEM 125kHz USB Proximity RFID Reader
Output shown in Notepad; 2747949856

Help. What number the RFID Reader read? :cry: :cry: :cry: :cry: :cry: :cry: :cry: :cry:

2

Scanning using Arduino and RC522 in HEX
UID tag number; 20 63 CA A3
Scanning using Arduino and RC522 in DEC
UID tag number; 32 99 202 163

These two numbers are the same thing. Each byte of the ID is expressed in decimal and hex
32 in decimal is 20 in hex
99 in decimal is 63 in hex and so on.

One thing I can't understand is that an RC522 is a smart card reader and is no way compatible with a OEM 125kHz USB Proximity RFID Reader. Unless you have dual cards, which are very rare. If so they will have different numbers on each type of tag.