The difference has to do with the period that that particular module is calculating. The Sources and Uses tab relates only to the cash flows modeled in the Development Module while the Equity CF tab relates to Development+Operations+Residual cash flows.
The difference between the two values is the amount of any operating shortfall during operations. This is most common when there is an operating shortfall during lease-up requiring the partnership to bring additional equity to the table post-construction.
One workaround to cover the equity requirement during lease-up is to inclue an operating shortfall line item in the development budget. By doing this, you essential borrow from the lender to cover the operating shortfall.
As a general rule of thumb, the Equity amount on the Sources and Uses tab would be the amount of ‘Hard Equity’ the partnership would forecast to need.