Problem in Creating Report.

Problem in Creating Report.

Hi everyone,
I'm trying to create some reports but reports are not accurate. I tried to create a task-related report in 2 different formats.
 1- how many Task done in the current month for deals with some custom fields of task.
2- Same reports with account wise.

But both reports are showing a different number of records. And also showing some records that are not available in the system.

Kindly help me.

Thanks & Regards
Shubham Agnihotri