What does it mean when my Product/CSC Code do not match with PDA/CSC Version?

I bought this SG-G900A online and was advertised as an unlocked International phone. When I tried to upgrade its Firmware using Smart Switch, I got an error suggesting that this device cannot be updated. Then, I tried to manually flash BOF3 update using stock recovery, and that failed too. So, I installed the Phone Info app and found the following:

General
----------
Manufacturer / Brand: samsung
Phone Model: SAMSUNG-SM-G900A
Device Type: klteatt
Product Name: klteuc
Knox Warranty Void: 0x0

CSC Code
------------
Product Code: SM-G900AZDACHN
Original CSC Code: CHN
Firmware's CSC Code: TGY
Active CSC Code: CHN / TGY
Available CSC Codes:
CSC Country: USA / US

Firmware
------------
Bootleader Version: G900AUCU4BOF2
PDA Version: G900AUCU4BOF2
CSC Version: G900AATT4BOF2
Baseband Version: G900AUCU4BOF2
Latest Firmware: Not Found
Kernel Version: 3.4.0-4432708
dpi@SWDD6014#1
32-bit
Java Virtual Machine: ART 2.1.0

Android
-----------
Root Existence: Yes
Android Version: 5.0
Build Number: LRX21T.G900AUCU4BOF2
Build Fingerprint: samsung/klteuc/klteatt:5.0/LRX21T/G900AUCU4BOF2:user/release-keys
Build Description: klteuc-user 5.0 LRX21T G900AUCU4BOF2 release-keys
Build Date: Thu Jun 18 18:03:47 KST 2015
Changelist: 4432708

Now, I wonder what exactly it mean when Product/CSC Code do not match with PDA/CSC Version? And, what are my options to make them identical?

Thanks.