"Map input bytes" vs HDFS_BYTES_READ

[Ted Yu]

In hadoop 0.20.2, what's the relationship between "Map input bytes" and
HDFS_BYTES_READ ?

<counter group="FileSystemCounters"
name="HDFS_BYTES_READ">203446204073</counter>
<counter group="FileSystemCounters"
name="HDFS_BYTES_WRITTEN">23413127561</counter>
<counter group="Map-Reduce Framework" name="Map input
records">163502600</counter>
<counter group="Map-Reduce Framework" name="Spilled Records">0</counter>
<counter group="Map-Reduce Framework" name="Map input
bytes">965922136488</counter>
<counter group="Map-Reduce Framework" name="Map output
records">296754600</counter>

Thanks