Custom sort not working

I'm having an issue with a custom sort in a matrix table as I want to have it in custom Periods e.g. 2022/23 Period 1, 2022/23 Period 2, 2022/23 Period 3, etc but what happens is that if I use Power BI to sort as it has text it would go in this order 2022/23 Period 1, 2022/23 Period 10, 2022/23 Period 11, etc.

I created a new table with one column for periods and the other with a reference order column e.g. 1, 2, 3 etc. I sorted the period column by the reference column then linked this table with the other table via period now the sorting order is random e.g. 2022/23 P8, 2022/23 Period 9, 2022/23 Period 4, etc.

Any suggestions would be extremely helpful. Thanks!!