An Engagement that has already been commenced for a given client (or company) can be modified at any time.

To modify an Engagement, click the Engagement icon for a given client as found in your Clients listing (the handshake icon, found towards the lower right):

Doing this brings up a display of their current Engagement, like so:

From there, click the "Modify..." button found at the bottom of that pop up window.

This brings up the Engagement editor pop up.  From there, you are free to modify anything about the Engagement, including:

• Increasing or decreasing the total allocation
• Changing the rules which dictate which appointments do and do not count
• Setting or resetting and notifications
• invoicing plan details, including the date of the next automated invoice