Typical data latency for small transactions is in tens of milliseconds, however there is no upper bound on data latency. Let me share this paragraph of the documentation with you:
Data latency from the time a transaction is committed on the primary to the time it is readable on a secondary depends on current log generation rate, transaction size, load on the replica, and other factors. Typical data latency for small transactions is in tens of milliseconds, however there is no upper bound on data latency. Data on a given secondary replica is always transactionally consistent, thus larger transactions take longer to propagate. However, at a given point in time data latency and database state may be different for different secondary replicas. Workloads that need to read committed data immediately should run on the primary replica.
Source is here.