In order to display user interaction time or the time it takes to answer prompts, a Strategy Enterprise Manager report must first be created, per the instructions in the following Strategy Knowledge Base document:
KB8902: How to create a report in MicroStrategy Enterprise Manager that will display each execution step of a job request along with the execution length of each step.
This report will display each execution step of a job request along with the execution length of each step. The screen shot below illustrates an example:

In the above report, the time to answer prompts appears in the Report Net Server step. A report job is first serviced in the Report Net Server and if the report contains a prompt, then the prompt answer will be collected at this step. The prompt answer is then passed onto the Resolution Server by the Report Net Server.