Could it be that you disabled or extended the period for session log files? These are included in the backup and if your logs grow, the backups will grow.
Or did you possibly enable debugging at some point? That may produce large files that at some point may end up in backups.
What may help is to check on your backups what is taking up the space. You can from a unix/linux based system (which you seem to be using according to your screenshot), run the tar zxcf command:
tar ztvf auto-backup-tips-2020-06-03-01-10-01.tar.gz
drwxr-xr-x root/root 0 2020-06-03 01:10 ./
drwxr-xr-x root/root 0 2020-06-03 01:10 ./PolicyManager/
-rw-r--r-- root/root 63 2020-06-03 01:10 ./PolicyManager/ne_periodic.state
drwxrwxr-x avendatomcat/appusers 0 2020-05-15 13:34 ./PolicyManager/sso/
-rw-r--r-- root/root 19 2020-03-14 22:07 ./PolicyManager/sso/onboard.yml
-rw-r--r-- root/root 58 2020-05-15 14:04 ./PolicyManager/sso/insight.yml
-rw-r--r-- root/root 17 2020-03-14 22:07 ./PolicyManager/sso/guest.yml
-rw-r--r-- root/root 83 2020-05-15 13:32 ./PolicyManager/sso/cppm.yaml
-rw-r--r-- root/root 132 2020-03-14 22:07 ./PolicyManager/sso/guest_operators.yml
-rw-r--r-- root/root 38760197 2020-06-03 01:10 ./PolicyManager/tipsdb.pgdump
-rw-r--r-- root/root 145 2020-06-03 01:10 ./PolicyManager/app-version.properties
-rw-r--r-- root/root 36351466 2020-06-03 01:10 ./PolicyManager/tipsLogDb.pgdump
drwxr-xr-x root/root 0 2020-06-03 01:10 ./Insight/
drwxrwxr-x appadmin/appusers 0 2020-05-23 15:55 ./Insight/admin/
drwxrwxr-x appadmin/appusers 0 2020-05-25 12:20 ./Insight/admin/sessions/
-rw-r--r-- root/root 3072 2020-05-23 15:55 ./Insight/admin/pref.db
drwxrwxr-x appadmin/appusers 0 2020-05-15 14:04 ./Insight/admin/customreports/
drwxrwxrwx appadmin/appusers 0 2020-05-15 14:04 ./Insight/reports/
drwxr-xr-x root/root 0 2020-06-01 00:01 ./Insight/reports/3001/
drwxrwxrwx root/root 0 2020-05-25 00:00 ./Insight/reports/3001/24-May-2020_22-00-29/
drwxrwxrwx root/root 0 2020-05-11 00:00 ./Insight/reports/3001/10-May-2020_22-00-11/
drwxrwxrwx root/root 0 2020-05-04 00:01 ./Insight/reports/3001/03-May-2020_22-01-01/
drwxrwxrwx root/root 0 2020-04-27 00:00 ./Insight/reports/3001/26-Apr-2020_22-00-50/
drwxrwxrwx root/root 0 2020-04-06 00:01 ./Insight/reports/3001/05-Apr-2020_22-01-04/
drwxrwxrwx root/root 0 2020-04-20 00:00 ./Insight/reports/3001/19-Apr-2020_22-00-26/
drwxrwxrwx root/root 0 2020-05-18 00:00 ./Insight/reports/3001/17-May-2020_22-00-22/
drwxrwxrwx root/root 0 2020-06-01 00:01 ./Insight/reports/3001/31-May-2020_22-01-04/
drwxrwxrwx root/root 0 2020-04-13 00:00 ./Insight/reports/3001/12-Apr-2020_22-00-15/
-rw-r--r-- root/root 2814449 2020-06-03 01:10 ./Insight/insightdb.pgdump
-rw-r--r-- root/root 146 2020-06-03 01:10 ./Insight/app-version.properties
-rw-r--r-- root/root 32 2020-06-03 01:10 ./cryptokeys
drwxr-xr-x root/root 0 2020-06-03 01:10 ./Extensions/
-rw-r--r-- root/root 56724081 2020-06-03 01:10 ./Extensions/yyyyy.extension
drwxrwxr-x root/apache 0 2020-05-15 12:53 ./Extensions/notify/
-rw-r--r-- root/root 145 2020-06-03 01:10 ./Extensions/app-version.properties
-rw-r--r-- root/root 32854474 2020-06-03 01:10 ./Extensions/xxxxx.extension
drwxr-xr-x root/root 0 2020-06-03 01:10 ./AppPlatform/
-rw-r--r-- root/root 20 2020-06-03 01:10 ./AppPlatform/server-modes.properties
-rw-r--r-- root/root 12 2020-06-03 01:10 ./AppPlatform/fips-config.properties
-rw-r--r-- root/root 161 2020-06-03 01:10 ./AppPlatform/app-version.properties
-rw-r--r-- root/root 61517 2020-06-03 01:10 ./AppPlatform/AppPlatform.pgdump
The third column, with numbers, are the individual file-sizes in bytes. If you compare between days, you should be able to see where the growth is.
This backup in the example is from a lab system, in production I would expect the backups to be larger.
Feel free to contact Aruba TAC support if you can't find out what is growing your backups, or if you don't know how to solve it.