The rule gives each item a date
The retention rule on a request gives every document and every written answer its own date. For a fixed period, the date is the day the item arrives plus the period. The first period counts in plain days, so 1 year is 365 days and a leap day inside it makes the date fall one calendar day earlier. Two items that arrive a week apart have dates a week apart. The notice your client agreed to states the rule.
For As long as they're a client, an item has no date until you mark the relationship as ended. It is then deleted in the next nightly run, or kept for the law's period from that date if you named a law. No row opens for it.
If you named a law, its period is a second stage. It starts when the first period ends, and a whole number of years counts as calendar years. A request that names a law never opens a row and is never offered a renewal, in either stage. See keeping documents under a law.
For example
Amaltas Deshmukh & Co sends Anita Deshpande a request on 1 July 2027 with a retention period of 90 days. She sends her documents the same day, so each has the date 29 September 2027. On 14 September 2027, 15 days before, a row for her opens in the Retention queue. If an admin chooses Renew with 90 days and Anita agrees, her documents move to 28 December 2027. That is 90 days after the date on the row, not after the day she agrees. If an admin chooses Keep because she is still a client, a review date 12 months after that decision is recorded, her documents carry that date and the row opens again 15 days before it. If nobody acts, her documents are deleted in the first daily run after 29 September 2027.