I want to try to replicate your issue and need a few more details.
Please correct me if I make any wrong assumptions.
I'm assuming that you're exporting to an Excel file(s).
How many columns of Detail does your Summary(s) contain?
It sounds as though you have entered your own Column Headings in the Summary's Page Header and are trying to align them with the columns of Detail below.
The 2 extra columns that you're describing in the Header Row
are likely the "Center Aligned" and the "Right-Aligned" page header fields that are created even without entries that define them.