Why, when entering the program, the study always starts with one number?

Question

PostgreSQL

Good afternoon.
There is a problem in one medical program that runs on pgSQL: when you start the program and when you create a new study, the same registration number 69 is constantly assigned. Subsequent new studies are assigned the following numbers 70, 71, and so on. You close the program, open it again and again the numbering starts from 69. I sin on pgSQL. What could be the problem there?
The program itself just crashes with nothing