1台One wait only, of another shape: for example a two-sided wait whose other end you already hold all four of. 1 tai.
Example
conc. kong四萬4
二萬2三萬356799234678一萬1
South wins on West's discard, East round, East deals.
Concealed hand 門清 1 + Single wait 獨聽 1 = 2 tai
In one line1 tai by default. Other values: ZSY (宅神爺) 2.
Conditions
Before the win, this was your only wait.
Waits are counted from your own tiles: a tile whose four copies you already hold or show cannot be waited on, and tiles out elsewhere on the table do not change your waits.