Running: iGO primo nextgen 9.18.27.717219 (Basarsoft) Oct 18 2017. Display: 1280x480, Android 7.1.1. Pongo skin, unit type? Made in China not any branch name but working very good in with the car, easy to install in MB C350e

Some one who can tell me where to find and how to change the scale for GPS "Altitude Correction". In my unit the correction scale is from -100 to 0 meter. Want to change this to -50 to +50 meter ( or -100/+100) Where and ho to do?