The challenge is that if the budgeted cashflow is non-zero, the Savings Budget can create an artificial sense of saving money. Imagine you have no income and a $100 total expense budget all put toward Groceries. If you spent just $50 on groceries, your budget would show $50 of savings carried to the next month… but, without income, your cashflow and net budget would actually be -$50.
The hidden calcs you are finding are meant to keep the budget and honest and may be helpful to you given that your expense budget is larger than your income budget.
This part of the thread may be helpful if you want more examples and detail.