"Must Spend" and "Like to Spend" are two separate budgets. You toggle between the budgets to see how each one impacts your plan.
So, if your "Must Spend" grocery expense minimum is $400 per month and your "Like to Spend" is $200 more, you should enter $400 in "Must Spend" and $600 in "Like to Spend."
There are many ways to leverage two budgets, below are a few ideas:
To model a necessary budget and one with comfort spending.
Use "Must Spend" to model necessities.
Use "Like to Spend" to model necessities plus discretionary spending.
To model a baseline budget and one with fewer expenses.
Use "Must Spend" to model your current budget.
Use "Like to Spend" to model a budget with less spending.