That's what I'm trying to figure out... it's not in the hints:-\
I believe it's similar to using "and" - so;
Ba trăm = 3 hundred
Ba trăm LE bốn = 3 hundred AND 4
What does tư mean?
Four and it's used often in place of bốn in counting or for ordinal numbering. E.g. Fourth place = hạng tư, Wednesday = (ngày) thứ tư. Tư is a corruption of tứ (the standard Sino-Vietnamese reading of 四 which means four in Chinese).