RSRT - Query Optimization - Not visible drilldown characteristics

Dear all,

Running transaction RSRT - Query Optimization - for a specific query and pressing "Technical Information" option, on the "Not visible drilldown characteristics" - "Free Chars", I got a YELLOW light. I thinks this is because I have 22 Free characteristics defined on this Query because this is a very Ad-Hoc query for flexible usage. How can this impact the performance? (that is in fact bad for this query!).

Thanks in advance

Best Regards