Run status mapping field is for mapping the test result's status values to ALM run status value. Yaml key represents the test result run status value. You should first set the status field in field mapping. Yaml value represents the ALM run status values. There are following status in ALM:
No Run
Passed
Failed
Blocked
Not Completed

Take following test result as example: <test-case name="ExampleTestOfNUnit.TestMultiplicationFail" executed="True" result="Failure" success="False" time="0.122" asserts="1"> Sample field mapping: run: status: "x: success" Sample status mapping: status: True: "Passed" False: "Failed"