Cam Shaft Change: What does it affect???

[NJ914]

When I rebuilt my '76 2.0L engine the cam shaft lobes were worn past the limit so I found a replacement.

I noticed that my old cam had a "-1" (or a "0")stamped on it. The new cam shaft came with a "+1" or "+2" on it. (Can't 100% remember...) I was told that my "-1" was not available and that the new one would work without any issues.

Is that true? Can someone comment on what the differences are with the numbers? Also if not true, what does it affect?