Are you talking about a release valve on the pump...
or were you pressing the valve on the shock? Also what brand of bike? some bikes mount the shock right side up (large end up) and I've seen a few that mount them upside down (large end down). There should be a very small amount of oil in the air chamber. This keeps the air seals lubricated. Usually though the oil sits on top of the air piston and doesn't go anywhere. However if the bike is stored upside down, or the shock is mounted that way it is possible to get some oil into the vlave on the shock. When you press on the valve the air pressure will blow a little oil out. Another possibility is the shock pump. The seals in shock pumps need oil as well to keep them working smoothly. I've had brand new pumps spray a little oil now an then as well. Anyway, it is not usually normal for the shock to blow oil out of the air valve, but it is possible for it to happen even if there is nothing wrong with the shock. But only under certain circumstances. So more info would be nice.