The procedure is:
Every time you enter a new room, use the Dungeon Crawling move (p.7). This will determine whether you find a special room, or just a regular one.
The d4 table is to determine further exits. So you roll a d4. If no special rooms have been revealed, look down the 0 column. If one has been revealed, look down the 1 column.
The idea is that as special rooms are revealed, potential further exits diminish. This is to reduce sprawl and to encourage backtracking so that the dungeon does not just feel like a linear straight ahead trudge.
Lmk if you have any further questions!