The most likely level of assets reflects the development of your assets if you implement the proposed financial plan in a disciplined manner and if return assumptions are met. Key for a disciplined implementation is a regular rebalancing of your financial assets in line with the allocation defined in your finanical plan and regular investments of savings into the recommended asset categories.
The worst-case level of assets corresponds to the level of assets at the end of the time horizon in case you implemented the financial plan in a disciplined manner, but there has been no return on your financial assets and your annual risk budget has been used up year after year by losses on your financial assets.