You can either display roman numerals (I ii V vi etc.) or the Nashville numbers (1, 2, 3 etc.).
They are basically the same, only the type of writing differs.
▶️ Numerals relation
You can also adjust the relation of the numerals.
When you have selected "Relative to root note of mode" (Default), the root of the mode will always be the "one".
For example, if you change the mode from major (Ionian) to minor (Aeolian) in the key if "C", the "C" will change from the degree I degree vi .
When you have selected "Relative to Ionian mode", the root will always be the Ionian relative.
For example, if you change the mode from major (Ionian) to minor (Aeolian) in the key if "C", the "C" will be the degree I even after changing to minor.
If a roman numeral is written in uppercase letters, it represents a major chord.
If it is written in lowercase, it represents a minor chord.
If it has a little circle next to it and is written in lowercase, it represents a diminished chord.