I have a yellow warning popping up with the warning "Docker high image disk utilization of 76%"
 

Clicking on container size it says a total of 18.1 GB

so dividing 18.1 by 76 multiplied by 100 means i have a container size of 23.8 GB
Is there a way to increase this or am i better off adding a container?

You should really look at why the image utilization is that large.  Container size will show the rough utilization per.  Most times it's a result of misconfiguration of a container resulting in say downloads from a download client being stored within the image instead of properly outside within /config etc

 

But, to increase the size, simply go to settings, docker, disable the service and increase the size and then re-enable.  

The biggest app i have is Tdarr, which i only installed today, and havent used yet.

 

Sabnzbd downloads to a shared download folder then moved to another shared folder.

 

Name                                       Container     Writable          Log
---------------------------------------------------------------------
tdarr                                         3.37 GB      1.16 GB      15.8 kB
binhex-krusader                         1.92 GB      35.6 MB       477 kB
H265ize                                    1.82 GB          0 B      14.9 MB
binhex-delugevpn                       1.30 GB      2.85 MB       115 kB
binhex-sonarr                             1.18 GB      46.6 MB      7.65 MB
binhex-minecraftbedrockserver   1.14 GB       279 MB       201 kB
binhex-radarr                              968 MB       154 MB      6.14 MB
binhex-radarr-4K                         968 MB       154 MB      2.20 MB
binhex-sabnzbd                          941 MB      33.5 MB      15.3 MB
Nextcloud                                  882 MB          2 B      13.3 kB
Plex-Media-Server                       633 MB       674 kB      96.0 kB
binhex-phantom                         605 MB          0 B      14.9 MB
FileBot                                      491 MB      28.2 kB       373 kB
MariaDB-Official                         414 MB          2 B       384 kB
MKVToolNix                               399 MB      24.7 kB       132 kB
ombi                                         330 MB       350 kB      1.58 MB
HandBrake                                327 MB      2.67 MB      28.2 kB
vaultwarden                              187 MB          0 B      5.95 kB
MinecraftBedrockEdition             119 MB       345 kB       319 kB
adminer                                    90.6 MB      12.1 kB       162 kB
NoIp                                         16.1 MB      5.45 kB      9.10 MB
---------------------------------------------------------------------
Total size                                   18.1 GB      1.87 GB      74.1 MB