I am curious about the serial number of a Dell SE2426HG monitor. Is it a 20 digit number or 23? Because on the box are 20 digits (CN-0Y0NYW-TV100-626-0LFV) and on the back of the monitor are 23 digits (CN-0Y0NYW-TV100-626-0LFV-A00   ). Is A00 is a part of the serial number or it is another thing? Which one is the serial number? Thanks. 

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