Report for 'My activities this month' showing incorrect data

Report for 'My activities this month' showing incorrect data

Hi there,

We have created a report for all users to run which should show their activities for the month. The criteria in the image below is what we have used, but the report is showing incorrect information when you run it. For example, one colleague is seeing tasks for contacts that he is not even the owner for. Please advise if the criteria needs to be changed or if there is a reason why the report isn't running correctly...

Thanks.