In DISTINCT mode the lenght of snapshot can be configured both server side and client side.

In your MetaData Adapter by the getDistinctSnapshotLength method you can specify the maximum lenght (in number of updates) of the snapshot for each item.

Client side, the setRequestedSnapshot method allow you to specify the requested length of the snapshot that every client wants to receive (you can also opt to not request snapshot delivery at all).
Please note that listening on onEndOfSnapshot event handler allow your client to be notified that all snapshot events for an item in the Subscription have been received.