WHMCS Onapp Configurable Options

I couldn’t seem to figure out how the whmcs configurable options worked in onapp, by looking through the code its become apparent that the module uses the sort order of the configurable option and adds that on to the base package, so for e.g. you have a base vps package set to 5Gb and wanted to offer upgrades to 10 and 15, you would create configurable options named: 5, 10, 15 but would set the sort order on these as 0, 5, 10 respectively, if the user chooses the 10 configurable option the resulting disk space would be 5Gb + 5 (the sort order value).