I don't believe that will work. Please don't mix or vape this until someone else with more knowledge than I have comments.
The most important point to consider is your final mix will be much higher in nic content than the 18 mg you desire. The reason for this is you are not using any straight PG or VG to cut the 48 mg/ml
juice. The 17% of flavoring is not sufficient to reduce the 48 mg/ml mic
juice to 18 mg. I believe t will create a final product that is close to 40% nic.
In the recipe you show in your original post, it assumes you will be adding straight PG and straight VG to the mix along with the 50/50 48 mg/ml mic juice to reduce the mic level to 18mg. If you try to use the mic juice to control both the mic level and the PG/VG ratio I believe either the mic level will be higher or the ratio in the end will not be 70/30. Hope someone smarter than me comes by soon to help out here.
As you can see in the recipe you are to add 3 separate ingredients Nicotine, PG and VG. The program does not allow you to specify that you desire to achieve a 70/30 ratio using only nic juice.
Edit:Rerun the recipe with just one of your nic juices either the VG or PG one, start with inputing it into the calculator at 100% PG or VG depending on which one you want to use.
Example:
48 mg/ml 100% PG
desired 18 mg 70/30 PG/VG with 17% flavor to make 10 ml
Nic juice (using your 48 mg/ml PG bottle) 3.7 ml
Straight PG 1.6 ml
Straight VG 3.0 ml
Flavor 1 1.5 ml
Flavor 2 0.2 ml