Ah, ok. Well, that's never going to be simple to represent, or work out, but it's a perfectly sensible requirement.
JIRA doesn't really support that directly, it's heavily focussed on issues over people. So it's better at saying "you spent this much time on issue X" than "person Y did Z".
What you need to look at is, I'm afraid, add-ons that can report on that sort of stuff better than the internal reports. I would start with a look in the marketplace for anything that says "timesheet", as that's really what "time spent by person" leads to.
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