Hooking up battery to newly rewired car

I just finished rewiring my car with the EZ wiring kit and the instructions say: connect the positive battery cable before connecting the negative cable you should check for current draw. This can be done easily with a test light connected between the negative battery post and the negative battery cable. No light equals no draw, if you have no draw or just a really dim light it is safe to connect the negative battery cable and start checking the system.

However, I have a bright light. I checked it with my meter and I have 12V. I am not sure I understand, though. Won't I always have that due to a few circuits being hot all the time ?