AutoCad 2D :: Cannot Rotate Dimension Text To Desired Angle

I'm making this diagram of the load condition acting on tunnels to explain a Japanese set of equations that are used for the structural analysis for tunnels:

load condition for EEM.jpg

But, there is one problem I have. I'm trying to set up the text for the dimension between the water table and the tunnel "Ha" to look horizontal.

However, if I click on the properties box and write 90 in the rotation box right next to where it says "text rotation," the dimension text does not rotate 90 degrees; if instead I try to rotate it 180° then it only rotates 90° (and in the opposite direction) instead of 180°. It doesn't matter how many degrees I choose, it won't rotate my dimension "Ha" to desired angle to make it look horizontal.

OK I know it's hard to explain my problem with just writing, so I've posted a few pictures:

In this one, the dimension is at 0°; I've only opened the properties box to attempt and rotate it: no rotation.jpg

Now I write 90 in properties box but the dimension text does not rotate at all; it remains at 0 as it is shown in the following image: 90 & no rotation.jpg

Next I try to rotate 180, just to see what happens; and it does rotate (only 90 degrees!): 180 rotates 90.jpg

I finally try to rotate the text 270 just to see if it rotates to desired angle and it does rotate (180 degrees from original position). As shown below:

270 last try.jpg

It doesn't matter how many degrees I choose, I cannot make it look horizontal.

How can I set up my dimension text "Ha" to look horizontal?