There are a couple of ways that you can do this.
If your data is grouped by status, you can just do a count summary of some unique identifier in your data. This will put the count in either the group header or the group footer for each status.
If you data is not grouped by status or if you want to show all of the counts in a summary at the end of the report, you'll do something like this:
1. For each status, create a formula that looks something like this:
If {table.Status} = 'Open' then 1 else 0
2. At the end of the report or at some group level you can then do a SUM of these formulas to get the count for each status.
-Dell