"An over-schedule override will be computed for each flight based upon each flight equal to one (1) paid trip, plus one tenth (.10) trip for each 5 minutes in excess of 55 minutes, truncated to the nearest 5 minutes. If this value exceeds the value under the non-standard formula, the flight will pay the override value"

TFP or time, depending which is greater. Once we go over the scheudled block, like if we are number 30 for departure from LGA (which is likely factored into the scheduled time) we get the overfly.