I am using \AMCcodeH{num}{2} for automatic student's association, so there are two numbers for the students to input.

My student's list looks like this:
num,,name
01,, StudentA
02,, StudentB
...
10,, StudentK
11,, StudentL


But when I export the marks in the report tab, for each students with code 01 to 09, there are two lines:
"Exam";"A:num";"Name";"Mark"
"15";"1";"StudentA";"6"
"";"01";"StudentA";"ABS";

Where 'ABS' is what I chose to represent absent students.

The extra lines stop appearing from code 10 onward, so it seems that AMC gets confused and looks for a grade for both code 01 AND code 1.
What's the best way to avoid that? I can edit the student's list of course, but I would prefer having no difference at all between the number I tell the students to tick and the list.
I'm also interested in knowing what the cause of the issue is.