You need a minimum of 520 paid contributions to get anything.
Then is about the average contribution over your history of contributions to determine the level of State Pension. So you divide the total number of contributions by the number of years from when you first entered the PRSI system until the Dec before your 66th birthday. If you first entered the Irish system at age 45, then your divisor will be circa 21. If your exact number of contributions were 520, then your average is circa 24.5. That should qualify you for an 85% Pension.
One question, if you entered the Irish system at age 45, how have you only got 520 contributions? If you have gaps (for which you got credits) then your average could be higher when you add 520 paid contributions plus your credits. That might push you into a higher band.