The "lines" are 0.076, 0.078, 0.079, so when a "Line get wiped" that's a big buyer taking out the whole "line"
The Gap is the difference between the top Buyer (0.068) and the bottom seller (0.076), so "the gap was closed" meaning, in this case a buyer moves to the sellers 0.075 or the sellers move to the buyer 0.069.
