This packet is designed to deliver a secondary clients transfer slot information to its primary host.

This is the packet format

[0x0384][ Que Status : S ]

The Que Status string is comprised of firstly currently in use slots then the total of potentially available slots as shown in the the following example.

"9001 1 of 1 available"

As you can see there is a 4 digit number followed by a message string. The number (9001 in this example) is not visible to the normal WinMX client user and is based on an index of 9000, this allows it to be used to indicate both "free" and "qued" slot positions, depending on whether the 4 digit number is above or below the 9000 base.
Although it may be obvious from the above, it important to clarify that the maximum amount of free up or down slots can only ever be 1-100 in a genuine client, zero slotted clients are of course fake.

Fake slot examples.
8900 100 in queue (0 of 0 available)
8921 79 in queue (0 of 0 available)
8989 11 in queue (0 of 0 available)

As can be seen above the famous "zero of zero" hack is mainly used by those who are too selfish to share anything.

Qued slot examples.
8917 83 in queue (0 of 1 available)
8930 70 in queue (0 of 3 available)
8946 54 in queue (0 of 1 available)
8954 46 in queue (0 of 1 available)
8961 39 in queue (0 of 3 available)
8978 22 in queue (0 of 4 available)
8986 14 in queue (0 of 2 available)
8990 10 in queue (0 of 1 available)  
8994 6 in queue (0 of 1 available)
8995 5 in queue (0 of 2 avail able)
8996 4 in queue (0 of 6 available)

Free slot examples.
9001 1 of 1 available
9002 2 of 3 available
9003 3 of 3 available
9004 4 of 4 available
9005 5 of 6 available
9006 6 of 6 available
9007 7 of 8 available

When the client is busy no slots indicator is sent out, another message is seen.

Busy slot examples.
Busy (7 in queue)
Busy (10 in queue)

From all this we can see that although the free slots are indicated by the 4 digits the total of currently available is not, however it can be very helpful to know that status messages starting with "8" are supposed to be red and those starting with" 9" are supposed to be green, "Busy" ones on the other hand are normally purple.