Update modules/server-compatibility/pages/server-compatibility-xdcr-mobile.adoc

Co-authored-by: Ben Brooks <ben.brooks@couchbase.com>

Author: iamfortune

modules/server-compatibility/pages/server-compatibility-xdcr-mobile.adoc

@@ -145,7 +145,7 @@ Testing and validation have focused primarily on two-cluster deployments.
 
 Clients maintain independent checkpoints for each cluster they connect to.
 
-When a client connects to a cluster for the first time, it begins replication from sequence zero, downloading all accessible documents.
+When a client connects to a cluster for the first time, it begins replication from sequence zero, checking which documents are missing and need downloading.
 The client stores this checkpoint locally, associated with the cluster's identifier.
 Subsequent connections to the same cluster resume from the stored checkpoint, downloading only changes since the last sync.
 This mechanism prevents redundant data transfer when clients switch between clusters.