A small question of Corruption_Test

In the test TableFileIndexData of file corruption_test.cc, i comment the line corruping data. then the check function failed, this is correct because the data are not corrupted. but if i change Value function as following,

the strange things happen.The Check functioin only get 9999 correct value and get a bad value.I'm very confusing.

The code of test TableFileIndexData are as following:

The result of test TableFileIndexData are as following:

Start by reading the TableFileIndexData test in corruption_test.cc, including its Check and Value functions, and compare the behavior with and without the corruption line. Reproduce the reported result before determining whether the unexpected value indicates a test issue or a LevelDB defect; the report does not define a specific change or completion condition.

Written by the indexing model from the issue text.