Forecasting in Float is currently done on a monthly basis. This means that even in a month where you have multiple cash movements for one chart of account category, you'll need to add up the total of what will come in or out of your business and enter it as a whole month figure, with one due date.
For instance, if I am expecting £20,000 to come from sales this month due to one £10,000 invoice due on the 5th, one £6000 invoice due on the 12th and one £4000 invoice due on the 21st, I would enter a £20,000 forecast in my Sales row with a payable date on the 21st (the last possible day the cash could come in).
Although your forecast will then show a £20,000 increase on the 21st of the month, when the invoices are created with due dates of the 5th, 12th and 21st, this will 'fill up' your £20,000 forecast and show the cash as being spread out throughout the month. So the sooner the invoices/bills enter your accounting software, the more accurate Float will be.
In 2017 we hope to expand this budget modelling to allow you multiple individual budgets/forecasts in one line within one month.