Recalculating your trades ensures that all charts are available for you in real time.
An example: your first trade was one year ago and you have trades in 6 different currencies. In this case, the system has to perform over 2.6 million calculations, since all the exchange rates from the previous year have to be multiplied with your input for each currency.
This process may take a few seconds.
If you call up a page, which relies on cached values, a message is displayed. With each new trade, the process starts anew.