Rosaire,

Absolute angle refers to the position of the stair to the stringer. If your absolute angle is 90 degrees, then you have a straight step.

Angle refers to how far from the absolute angle position is the step. Therefore, a angle of 0 degrees is seen when the absolute angle is 90 degrees. This means that a movement from a straight step of -5 degrees sees an absolute angle of 85 degrees.

https://wooddesigner.org/help-…..arameters/

The Left and Right angle is usually seen on circular flight stairs. This refers to how many degrees of a circle you need to cut the stair on each side.

https://wooddesigner.org/help-…..r-flights/

Let me know if you need further explanation.

Regards,

Isaac