Webpage and Apple App show different GPIO

I have a Raspberry Pi Model B which is running an 8 channel relay. This works fine except one GPIO.

On the website is shows it has GPIO 21 which works.

However on the mobile app its showing GPIO 27.

I do think I know what the issue is. I built this on a Raspberry 3 then moved the SD card to the Model B.
Is there a way to change this without reinstalling?

Shows up as GPIO 27 on my phone too. I think this is likely just a typo. Tagging @bestes and @rsiegel

That would explain it. Unfortunately it doesn’t work from the App but does from the webpage.