Are you certain that the Z-zero is correct at the surface of the workpiece?
Also, once you load the code, switch to the Toolpath tab.
In the upper right hand corner, you can confirm the limits of the program that is loaded.
DROs can change rather quickly at times so you might have missed it or it could be updating at a rate the picks numbers along the way without reflecting every single move. For example, I was drilling some holes today and even though I know it was pecking in at 0.1" increments, the DRO would show -0.0987, then start retracting, then go down to -0.1997, etc. I am certain the DRO wasn't seeing all the numbers.