Question about netcdf file

[Chi <chi@xxxxxxxxx>]

Hi there
   I have a 3D netcdf file (lat/lon/depth) and it works perfectly with LAS. The longitude range is from 30.5W to 27.5W, the step is 0.5.
   Then I did a test. I used "ncdump" to dump the netcdf file, changed the longitude to from 30W to 27W, the step is still 0.5. Then I added it into las. 
   My question is that when I made a slice out of the modified dataset at 27W, should it return the same image/data as 27.5W at the original dataset? They have the same index in the longitude dimensions, so I guess they should. 
   Anybody can help me about this?
   Thx, Ding