The Data Packet is a location in application storage where the physical mouse device driver returns to the caller the following data:

┌─────────────────────────────────────────┐
│Field             Length     C Datatype  │
├─────────────────────────────────────────┤
│Element Count     WORD       USHORT      │
├─────────────────────────────────────────┤
│Queue Size        WORD       USHORT      │
└─────────────────────────────────────────┘