Steps to replicate the issue:

• Go to Category:Islamic organizations by year of establishment on English Wikipedia. You will see that all categories sorted by numbers (years indeed) are sorted under "0–9"; no matter what number the sort-key starts with.
• Now go to corresponding رده:سازمان‌های اسلامی بر پایه سال بنیان‌گذاری (میلادی) on Persian Wikipedia and see the sorting method. As you can see, categories for 3rd millennium (2000 onwards) are sorted under the number character "۲" and categories for 2nd millennium (starting with the number "1") are sorted under "۱".

What happens?:
Persian numbers used as category sort-keys are merely considered as characters instead of numbers, and thereby, for example, in this category, the sub-category for the year ۵۶۵ (565) is listed under ۵ after ۲۰۲۰ (2020).

What should have happened instead?:
All pages (sub-categories and other types of pages) sorted by Persian numbers (۰۱۲۳۴۵۶۷۸۹) should be listed under "۰–۹".
Note: Just like the default method for English numbers, ۵۶۵ (565) should be listed before years like ۱۹۹۵ (1995), not after it just because 5 is greater than 1. in other words, the whole integer (565) should be considered for sorting, not just the first number (5).