It is a mental attitude that:
1) being upright; not lying (for example by telling the truth);
2) not cheating (for example in a game, by following the applicable rules);
3) sincere; ikhlas.
So it is interpreted as an attitude that reflects the compatibility between heart, words and actions. What is intended by the heart, spoken by the mouth and displayed in action is what really happens and is true. This is in line with the values of Prince Diponegoro who prioritized honesty, reflected in the nature of the struggle against falsehood and evil.