Doubts Regarding Tape Library .. Please clarify

So you sound like you have several Media servers sharing some or all of your configured 10 tape drives.

You need to clarify this. But it is more than likely that all your media servers that write to the 10 tape drives are sharing these drives amongst each other.

Each Media Server sharing the tape drive device will be listed when you select each drive.

If you are new to netbackup then can offer this good advice and specific guide from the docs set to be read-

discusses shared storage.

Enterprise Support - Symantec Corp. - Symantec NetBackup 7.1 Shared Storage Guide

MISSING PATH for me normally means that the device file/path has changed since the last device configuration and might be worth running the Storage Device Configuration Wizard in the Console GUI to fix.

SCAN-TLD means this is the master control device host for that specific tape drive. Something has to look after locking and sharing of the drive amongst the hosts its configured for when a backup is requested so there is no race condition for the same drive.

ACTIVE means there is a tape drive operation in progress. You want to switch to Activity Monitor and see in the detail of any job if its using that device.

DOWN means the drive is could be down on some or all shared device hosts.

MIXED means some shared device hosts have it in TLD some have it DOWN or in another state.

IDEALLY you want to see 1 x SCAN-TLD and the rest in TLD mode

Good luck and learning.