`latency` parameter indicates when the target last synced up with the source. For example, here it's 201 and 202 for the two databases as shown in the picture below. It means that the changes that occurred in the last ~200 seconds at the source are yet to be synced to the target. At this point, writes to the source can be stopped and cutover initiated. In case there's heavy traffic at the source, it's recommended to stop writes first so that `Latency` can come close to 0, and then cutover is initiated. The Cutover operation applies all pending changes from the source to the Target and completes the migration. If you trigger a "Cutover" even with nonzero `Latency`, the replication stops until that point in time. All the data on the source until the cutover point is then applied to the target. Say a latency was 15 minutes at the cutover point, so all the change data in the last 15 minutes applies to the target. The time taken depends on the backlog of changes that occurred in the last 15 minutes. Hence, it's recommended that the latency goes to zero or near zero, before triggering the cutover.
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