you are thinking compression ratio.
You want your numbers to be around 160 on each cylinder.  I am not 100% sure of the number off hand but it should be higher than 140 for sure.  All 6 numbers should within 10% as well.
You want something like this 
	
	
	
		
		
		
			
		
		
	
	
The gauge threads into a piece that threads into your spark plug hole.
You want to warm up the car first to operating temperature, let it cool down for ~2-5 mins, remove all 6 plugs, disable your ignition system, than start testing on number one.
You should hold the gas to the floor and let the engine crank over about 5-6 times on each cylinder.
Something like that.