doc: mention test runner retry attemp is zero based

Author: MoLow

doc/api/test.md

@@ -3875,7 +3875,9 @@ added: v25.0.0
 
 * Type: {number}
 
-Number of times the test has been attempted.
+The attempt number of the test. This value is zero-based, so the first attempt is `0`,
+the second attempt is `1`, and so on. This property is useful in conjunction with the
+`--test-rerun-failures` option to determine which attempt the test is currently running.
 
 ### `context.workerId`
 
@@ -4248,9 +4250,9 @@ added: REPLACEME
 
 * Type: {number}
 
-The current attempt number of the suite. Used in conjunction with the
-`--test-rerun-failures` option to determine the attempt number of the current
-run.
+The attempt number of the suite. This value is zero-based, so the first attempt is `0`,
+the second attempt is `1`, and so on. This property is useful in conjunction with the
+`--test-rerun-failures` option to determine the attempt number of the current run.
 
 ### `context.diagnostic(message)`