Update disk_check.sh

more reasonable number to delete

scripts/disk_check.sh

@@ -9,9 +9,10 @@ if [ "${used//%}" -ge 95 ]; then
     purge) echo "Removing oldest data"
         cd ${EXTRACTED}/By_Date/
 	curl localhost/views.php?view=Species%20Stats &>/dev/null
+        filestodelete=$(($(find ${EXTRACTED}/By_Date/* -type f | wc -l) / $(find ${EXTRACTED}/By_Date/* -maxdepth 0 -type d | wc -l)))
         iter=0
         for i in */*/*; do
-            if [ $iter -ge 250 ]; then
+            if [ $iter -ge $filestodelete ]; then
                 break
             fi
             if ! grep -qxFe "$i" $HOME/BirdNET-Pi/scripts/disk_check_exclude.txt; then