I paid a brief flying visit on Saturday whilst in the area for a meeting. There are two sections I3. The one nearest the gate ends at around 450, so I assume 998 is the other one at the far side which I didn't have time to reach. There is only one section D1, but the highest number I found there was also around 450, though there are lots of unmarked graves and unnumbered or difficult-to-read gravestones. I'll try to get back there in a few weeks time and with more time to search. If anyone can get there earlier, PM me and I'll supply some clues.
The time wasn't wasted as I did find a request from another site.