How can I create an algorithm to determine if the certificate presented by a candidate in an interview was issues by university X?

Design an algorithm to find or determine the certificate presented by a candidate in an interview was issued by university X. Assume that the certificate issued by the University X is coded as 200001, 200002, 200003 till 205000, where the first 2 digit indicate the year of insurance and the remaining digit indicate the serial number.

I tried and followed the standard algorithm approach

1. Understand the problem to be solved
2. You decide on

• computation means
• will your solution be exact or approximate
• what data structure are you using
• algorithm design techniques to be used

3. Design the Algorithm; specifying the algorithm using natural language/pseudocode/flowchart/UML diagram
4. Proof of correctness of the algorithm
5. Analyze the algorithm; this determines the performance of the algorithm in terms of time
6. Code the algorithm; translate algorithm to computer programming language of any of your choice.

but am having issues with step 3