What does the log output from openstreetmap-tiles-update-expire/render_expired mean? - rendering

Question

i am using the script from https://github.com/openstreetmap/mod_tile/blob/master/utils/openstreetmap-tiles-update-expire which is running inside the docker container of https://github.com/Overv/openstreetmap-tile-server.
I modified the script to always render expired tiles.
I changed the following line to:
render_expired --map=default --num-threads=8 --min-zoom=$EXPIRY_MINZOOM --max-zoom=$EXPIRY_MAXZOOM -s /run/renderd.sock <"$EXPIRY_FILE.$$" 2>&1 | tail -8 >>"$EXPIRYLOG";
Where
EXPIRY_MINZOOM=8 and EXPIRY_MAXZOOM=19
Now i am confused of the long rendering times and the generated logs of this command.
The logs say : Wrote 2616400 entries to expired tiles list and it starts rendering with render_expired. After 11hours of rendering it says:
Total for all tiles rendered
Meta tiles rendered: Rendered 225518 tiles in 46397.42 seconds (4.86 tiles/s)
Total tiles rendered: Rendered 14433152 tiles in 46397.42 seconds (311.08 tiles/s)
Total tiles in input: 2616400
Total tiles expanded from input: 248012
Total meta tiles deleted: 0
Total meta tiles touched: 0
Total tiles ignored (not on disk): 22494
Can someone explain these logs to me and tell me where the amount of Total Tiles rendered: 14433152 come from? I guess this is the reason for the long rendering times.
My import was a merge of 4x .osm.pbf files and their .poly files (Germany, Switzerland, Austria, Liechtenstein).
I prerendered all tiles with render_list_geo.pl up to Z19 before starting the update script.
Thank you very much.
piggeldy94