Monthly Contribution/Savings Builder
I am puzzled or misunderstand how the "Monthly Contribution/Monthly Savings Builder" works. example: I have set a goal for "Camp" of $100 per month; if I don't contribute anything in May, then in June it still asks for only $100 to meet goal, shouldn't it be $200 since I didn't contribute in May and therefore need $200 to meet my goal?
The option then seems to be to set it up as a "Spending Goal: By Date".
Maybe it's the terminology to me but it seems to me if I have a goal of monthly contribution and don't make it one month, I would want to try and make it up the next month.
Monthly (Savings) Contribution only looks at one thing: how much is in your Budgeted (middle column) box this month. It is not at all backwards or forwards looking. It doesn't care if you budgeted more or less than your goal last month or if you plan to budget more or less next month. It also doesn't care if you budget $100 and then spend $100 instead of save it, and it doesn't care if you budget $200 this month instead of $100. Next month it is going to ask for you to budget $100 again, full stop.
The Build Your Savings: Target Balance (By Date) goal asks you how much in total you want to SAVE (e.g have Available), and by when, and it will calculate how much you need to budget each month to meet that goal. If you budget less than that amount one month, it will recalculate across ALL the remaining months, not just double the next month.: if you want to save $600 in 6 months, it will tell you to budget $100/mo. If you skip the first month, it will tell you to budget $120/mo for the next 5 months. If you only budget $50 the first month, it will tell you to budget $110/mo for the next 5 months, etc. If you SPEND any of the available money before the goal is reached, this will also recalculate the goal because you told YNAB you want to have $600 available 6 months from now.
The Plan Your Spending: By Date goal basically keeps a running total of how much you have budgeted toward your goal, and will recalculate if you budget more or less in a given month, but does not recalculate the goal if you spend some of it. This is useful for things like Christmas where you plan to spend $600 on gifts in December, but you may find the perfect thing on sale in November or October.
"Making it up" requires a defined endpoint / trajectory, which is an entirely different goal (Save By Date, as you mentioned). Monthly Contribution is exactly what it says on the tin -- put in $X this month.
One example is a roll your own "budget-billing". Set a Monthly Contribution for the average of your Electric bill (yearly total / 12). Assuming you start when spending drops below average, this will build up a surplus in the category that you will naturally consume in the above average months. A consistent budget entry makes it easier to plan all your other budget entries. I do this with utilities, auto fuel, kids activities, etc.; basically everything that varies seasonally.