How can I change a tertiary mobile phase gradient to binary?

If there are only 2 solvents simply prepare the starting mobile phase conditions as mobile phase ‘A’ and the final mobile phase conditions as ‘B’ and run a gradient from 100% A to 100% B.

For example, taking application 18842, mobile phase A would be 10 mM ammonium formate pH 3.2 in H2O/ACN (10:90) and mobile phase B would be 10 mM ammonium formate pH 3.2 in H2O/ACN (50:50).