I think I got the point.

For example in diffserv3: tdiff values -2, 2, -1 for tins 1, 0, 2, then:

"if (tdiff<=0 || tdiff<=best_time)" returns best_time -1 and tin 2. Highest priority tin with packet overdue.

"if (tdiff<=best_time)" would return best_time -2 and tin 1. Not the highest priority tin with packet overdue.

Thank you,

George