In sequencing papers, there always are figures like this :

What I don't understand is that ,why they only report 6 columns, I think there should be 12 columns.

For example, there are 6 columns in the figure,

T>G/A>C, T>C/A>G, T>A/A>T,C>A/G>T,C>G/G>C,C>T/G>A

I think there should be

T>G/A>C, T>C/A>G, T>A/A>T,C>A/G>T,C>G/G>C,C>T/G>A +

A>C/T>G, A>G/T>C, A>T/T>A, G>T/C>A, G>C/C>G, G>A/C>T

I think the number of T>G in the positive strand and the number of A>C in the positive strand is not the same.

I am confused about this, could someone help me, thanks in advance.