Citizenship

Hi all hope you are well :
I have stamp 4 eufam i wonder if i want to apply for citizenship , is the 5 years reckonable start calculated since the first stamp wich granted 3 months when we came to Ireland or since irp card was issued ? Thanks

Following is an extract from a document from ISD

"Residency permissions are evidenced by stamps in your passport, while additional periods may be covered by letters issued by Immigration Service Delivery granting you permission for a specific period from or to a specified date. Please note that any failure to register with the Garda National Immigration Bureau within a reasonable period will be taken into account in assessing your application."