The Offset by Normal Window is used to interactively move the selected vertices along the vertex normal. This only affects vertices that are connected to a triangle. It is made up of a text entry box for the max distance with a slider and a text entry box for the percent value.
The vertex normal is the averaged direction of connected triangles. It is not affected by the group smoothing and max angle.
The offset to move the selected vertexes is calculated by the max distance scaled by the percent value. The percent value slider allows for better interactivity.
The max distance is the value to move when the slider is set to 100%.
The percent value ranges from -100 to 100 and starts at 0. A value of zero is the starting shape of the selected mesh. You can drag the slider left to decrease the value, or drag it right to increase the value. You can also change the value by typing a new value into the text box next to the slider.
Press Ok to keep your changes or press Cancel to ignore any changes.