How will I know my direct reports have shared their productivity with me?

If your employee has shared checked in their productivity before their 1-on-1, you can view it inside the 1-on-1 page
Open the recent upcoming 1-on-1 with them. As you open it, the first thing you will see is that respective employee's productivity rating and response on the right side

Alternatively, Peoplebox also sends you a mail when your employee(s) share their productivity with you. The mail consists of your employee's response and also their marked reason for high or low productivity