Gs1 Databar With Ean 13 - Extra Digit Added フォローする

Hello,

I am trying to create a GS1 DataBar with GTIN13 + serial number. It looks like the GS1 Bar "wants" to have 14 digits, whereas we use the GTIN13.

My bar should look something like this:

(01)xxxxxxxxxxxxx(21)xxxxxx

Question 1: The GTIN13(ean) after the (01) automatically receives an additional digit. I want to have my 13 digits here, but the system creates an extra digit in the end.  Anyone know why?

Question 2: Is it ok to use "only" 6 digits in the serial number (after the (21) )? I see some have 12, but it is of course only to put in zeros, I assume... Any rules on this?