When Float is importing payments from your accounting software it distinguishes between 2 classes, reconciled and unreconciled. Reconciled payments are those that have been matched up with the corresponding invoice, bill, receipt etc. While unreconciled payments haven't yet been matched up.
In Float reconciled payments are imported across and displayed in the cash flow, however unreconciled payments are not. The reason being that these payments are not yet classified so can't be assigned to a cash flow row just yet.
Having unreconciled payments in the accounting platform can throw off the historic opening and closing balances in Float. This is because Float takes the bank balance as of today and works backwards adding/subtracting the reconciled payments to generate historic balances, as unreconciled payments aren't included in the calculation at this point the historic balances can be thrown off by this. So it is important to keep up to date with reconciliation so Float can pull across all the correct info.
For more info on reconciling payments in the different accounting platforms check out the help sites below: