Some partitions not mounted

WD Legacy Products WD TV Live & Live Plus
1

I have a 500 GB External Hard Drive connected via USB.  The drive has 4 fat32 partitions.  But, only 2 partitions mounted.

Any ideas why?

2

How are the two partition identify by the WD TV, USB 1 and 2?

3

They have the label of the partition.  All of the partitions have labels, but only two are available.