How to get SSRS report to show Downtime per user correctly

Question

I have created a report in SSRS which displays data from the below table. This table groups data by the hour.

the the report sums of the total quantities each user did per hour, then with a totals colum at the end for the whole day

below is a preview of the report

my issue is, for the column 'DownTime', this shows the time between the current time and the last time each user did something.

When I add the column Downtime to my SSRS report, it is adding up the downtime for each time the person appears in the table. I only want this column to fetch the the number from downtime once for each user.

For example "bob" might have 5 minutes since he last did something, so the table will show Downtime 5 for "bob".

However if bob has many actions overs several hours so there are 6 columns with "bob" in it in the table, then my column "downtime" on my ssrs report will show 30 minutes downtime (5minutes x 6 entries in the table).

My downtime column is not set to sum(downtime) it's only downtime, i'm not sure how i can get the report to show only the value once and not multiple it for every time they appear in the table, can anyone help, I can't think what to do to get what i want?

thank you