It’s a bit complicated and can depend on your specific household situation, but at its simplest, the Groups will appear exactly in the order they do on the website, where the Group order is determined by the order of the Envelopes and their corresponding Group names there.
If you’ve ever changed your Envelope order on the phone app though, it’s possible it could be a little messed up, because making changes on the phone will overwrite the original order (on the app only).
…I’m not sure that made a whole lot of sense, but tl;dr it usually matches the website, unless you’ve changed it before.
If you’ve changed it before, or are simply still confused and would be helped by us looking specifically at your setup, just shoot us an email at support@goodbudget.com with your Goodbudget login email and a screenshot of your Envelopes tab on the phone and we’ll take a closer look.