Open page "Setting Concurrency and Timeout Factor" under "Editing Quick Set Values" node in section "Concurrency" of online help.
Help says that "The default range of values used by the harness is from 1 to 50" but actually max possible value for concurrency is 256.
Note: This bug is actual for the page "Editing Concurrency and Timeout Factor" under "Editing a Template" page in GUI online help
Note: this bug is actual for the page "Setting Concurrency with concurrency" under "Setup Commands" node in "Contents" tree of CLI online help.