Did my response not show up, was it confusing...
Nic mg/ml is a personal preference, you may need 12mg/ml, or 6mg/ml might make you Nic sick. No way for us to know.
The majority of folks using subΩ DTL delivery device use 3mg/ml - 6mg/ml.
Are you aware of the difference in method of vaping MTL vs DTL.
You'll have to experiment to see what works best for you.
If you bought 1 bottle of 0 Nic & 1 of 6mg/ml, you could try the 6 right out of the bottle and mix the 24 down to 12 using equal parts of the 24 & 0.