That would be TDC on the compression stroke of course. It also has a TDC on exhaust stroke which would be 180 or half a turn out on the distributor. YTou have to pull the #1 spark plug and stick your finger in the hole while the engine is bumped over to find which TDC you are on. Also getting the distributor to fall back into the oil pump drive slot may require using a long screw driver to turn the shaft until you get it in the correct place so the distributor will fall all the way in.