three_SIG0 = {SIG0[*3]}

This sequences matches against 3 consecutive matches of SIG0. Note that this sequence could also have been specified as {SIG0;SIG0;SIG0}, but this gets awkward for specifying large numbers of repetitions of a pattern. There are no cases where SIG0 is high for 3 consecutive cycles, so all the match attempts eventually fail. The transaction record at time 200 holds for the first 2 cycles, then fails in the third cycle. Because it takes 3 clocks to fail, and two new matches are attempted during this time, two overflow signals are required to display all the transaction records without overlap.