Almost instant. After you have updated your data within Once Setup, press the Upload data button.
Next, in Once Mobile, go to Settings, and press Check for new data.... The data that you uploaded will be downloaded to Once Mobile, ready for use straight away.
Note: Both Once Setup and Once Mobile will need to have an internet connection and a valid subscription. However, it doesn't matter if Once Mobile isn't connected to the internet at the time that you upload the data from Once Setup. The Once Mobile users can check for new data at any point in the future once they have an internet connection.