Question about 20000 rials iran banknote

Hello!
I was checking Iran's banknotes and in 20000 rials banknotes there is 7 years in date bar but three of them are the same banknote with same signatures can someone explain why there is 7 bars but not 4 bars instead? (I am really new to banknote collecting)
you can check the page in here: https://en.numista.com/catalogue/note206243.html
1. Valiyollah Seif & Ali Tayebnia
2. Abdolnaser Hemmati & Masoud Karbasian
3. Valiollah Seyf & Masoud Karbasian
4. Abdolnaser Hemmati & Farhad Dejpasand

Bank Note Museum has what would appear to be proper listing, 4 notes, only a & b with Krause numbers, all ND.

http://www.banknote.ws/COLLECTION/countries/ASI/IRN/IRN0153.htm

Will