In den Page Format dialogs Margin area the unit is mm. In the Left/Right fields a dialog saying “0 to a maximum of 10” is allowed, in the Top/Bottom fields “0 to a maximum of 2” is shown when a too large value is entered.
In fact the accepted maximums are 9 for Left/Right and 1 for Top/Bottom!
So the restrictions described do not fit and of course the restrictions are much too low in mm units!!!