You could develop your own definition of timely but in reality, 8.3 and 8.5.2 is asking what amount of time your organization allows for the action to occur.
In 8.3 you need to define the time period allotted to make the report to the customer that they may have nonconforming product. Usually, but not always, this is specified within the customers contract.
8.5.2 You need to define the allotted time given for responding internally to corrective action and the anticipated time the corrective action will be fully implemented. Usually the customer will tell you when you must responded to their corrective action request but you still need to define a time period in days if they don’t.
Word of caution here, when specifying a time period in days make sure you indicated business days and not calendar days. With calendar days weekend days count.