Type in what each space actually holds right now.
The usual figure is the baseline. Type over any month to change just that month. Changed cells are highlighted.
Decide which space gets what. Anything not allocated is flagged.
Each cost comes out of a space. Tick when it's actually gone.
What life costs once you're in. Starts the month after completion.
Starting from what survived completion. The top one fills first, then it cascades.