When you use the File Manager in DirectAdmin to upload files to your server, you will see the Max Filesize is set to 10.0 MB. The file upload manager won’t let you upload a file larger than 10MB. If you are the admin of the server, you can easily change the max upload size.
Login to DirectAdmin as Admin, then scroll down to the Advanced Features at the bottom section. You can then find the Administrator Settings.

Click to open the Administrator Settings. Scroll down until you reach the Server Settings (will restart DirectAdmin) section, where you can see your server’s hostname, name servers and other information. You can find the Max Request/Upload Size (bytes) option. The default is set at 10.0MB. It refers to the maximum file size that can be uploaded through the control panel. You can then set Max Request Upload Size (bytes) to your needed value, say 20MB, 30MB, 40MB, etc. Click Save button at the bottom of the page to save the change. Note that this change may take up to 1 minute to take effect.Wait a 1 min, then login DirectAdmin as regular user, you should find the Max Filesize is now set to the new value.

Ui is not realy good. And why administrator is not available