This came from the Hatcheck forum, (with some parenthetical adds from current matchers):
"Early: 1st at all calls. (He means always first at first call)
Early Presser: 2nd at first call. (runs no more than half a length off lead - so it was trying for the lead; any more than 1/2 back and horse is a presser
Presser: 3rd at first call.
Sustained Presser: 4th, or 5th at first call.
Sustained: at 6-9 at first call.
Late: 10th, or more at the first call.
The Hat"
Hope this helps,