0     8     16    24    32    40    48    56
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|         SIZE          |       PURPOSE (0x03)  |
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|                   TIMESTAMP                   |
+-----+-----+-----+-----+-----+-----+-----+-----+
|       ZONE TYPE       |     ZONE KEY          /
+-----+-----+-----+-----+                       /
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+