Sitemaps not including all URLs

[Joel]

We recently rolled out a DSpace 6.x to 8.1 upgrade and while it's been mostly smooth, regenerating the sitemaps are not creating as many files as I expect. The HTML files are limited to exactly 100 files in total which I find suspicious. The command:

$ export JAVA_OPTS="-Xms4g -Xmx16g -XX:-UseGCOverheadLimit -Dfile.encoding=UTF-8"

$ [dspace]/bin/dspace generate-sitemaps

runs without errors and completes quickly.

Is there some sort of built-in limit that is stopping at this number? Google's search console recognizes the sitemaps but shows exactly 31,112 URLs, bu I expect to see somewhere like 111,000 URLs which is about what Google reported when I was still on DSpace 6.

Does anyone have any suggestions on what is going on?

Thanks!