id	definition
A1	Bottom level first position from front end.
A2	Bottom level second position from front end.
A3	Bottom level third position from front end.
A4	Bottom level fourth position from front end
A5	Bottom level fifth position from front end.
A6	Bottom level sixth position from front end.
A7	Bottom level seventh position from front end
B1	Second level first position from front end.
B2	Second level second position from front end.
B3	Second level third position from front end.
B4	Second level fourth position from front end.
B5	Second level fifth position from front end.
B6	Second level sixth position from front end.
B7	Second level seventh position from front end.
C1	Third level first position from front end.
C2	Third level second position from front end.
C3	Third level third position from front end.
C4	Third level fourth position from front end.
C5	Third level fifth position from front end.
C6	Third level sixth position from front end.
C7	Third level seventh position from front end.