Open new blank OOo Writer document.
Increase indent of first paragraph by means of button on Formatting toolbar.
The paragraph indent is now 1.25 cm.
Add a tab stop at about 3 cm by clicking in the horizontal ruler at the top
of the document.
Add a second tab stop at about 16 cm by clicking in the horizontal ruler at the
top of the document.
Open the tab stop editor by double clicking the 16 cm tab stop in the ruler.
In the position field, select the tab stop closest to 16 cm. Change the fill
character to all dots.
Close the tab stop editor by clicking the OK button.
Watch the 16 cm tab stop in the horizontal ruler shift to 17,22 cm.
It appears that at some point in the tab stop calculation the tab stop
position gets calculated relative to the indent.
Note however that the 3 cm tab stop remains on its correct position.