Problem with dimensions

I use the tools-->Dimension Vertical and a get the value 0.01 when my coordinates tell the distance is actually 0.250.  How does this happen? How to fix this?

In Options - Current Drawing Preferences  -  Dimensions - Length Factor you probably have a value other than 1. The use of this factor is to manipulate the dimension reading. But the real length stays the same.  

Be careful to dimension the intended object and not just some random location.