Dual Dimensions appear to be floating above the dimension line.Dimension text with Dual Dimensions appear to be above the dimension,appearing like a fraction and the change dimension tool has noaffect on the lower margin values.Product: MicroStation V8 2004 EditionVersion: 08.05.02.35Area: Dimension/Measure
The key-in: CHANGE DIMENSION JUSTIFICATION FROMSTYLE can be used.
http://communities.bentley.com/communities/other_communities/askinga/w/askinga/change-dimension-text-justification