I agree with
@chanelvaps. I posted a similar question years ago, and it was explained to me that because of the add'l ingredients in e-liq (such as PG and VG) the end result of the nicotine level will be reduced. A simple (but maybe not exact if the two liquids have differing PG/VG ratios) equation to use in this case is the nic levels of liq1 + liq2 divided by 2. Basically an average calculation.