I took my rc10gt to my lhb and they adjusted my diff. Now when the car is off, if i spin one wheel the other one goes the same way, and if i try to hold one wheel and spin the other it wont let me.Does this mean its to tight?

yeah it is to tight
but i have been running my xxx-nt that way
you can do some impressive donuts with the diff locked

Sound like it is too tight to me. I don't think it will wreck anything to run it like that, but it won't handle as well, and you will prob have to rebuild the diff sooner.
It is better to run it too tight than too loose. If you run with it too loose, the diff will slip instead of the slipper clutch, and will generate ALOT of heat and melt the diff gear in the tranny in very short order.

Thanks for the help.

i only need to bearly turn it to ajust it