SubscriptionServices - what is "AvailableSequenceNumbers"?|OPC Certification and Interoperability Testing|Forum|OPC Foundation

This is from conference unit - SubscriptionServices.

Publish()

The following checks are performed for all valid parameter tests:
• Response.ResponseHeader.ServiceResult is Good.
• Results are not null or empty when provided with acknowledgments, and the results length matches the subscriptionAcknowledgements length.
• The availableSequenceNumbers are in numeric order.
• Verify acknowledged sequence number(s) are not returned in availableSequenceNumbers.
• Any Publish response containing DataChange notifications for any given subscription will provide the SequenceNumber in the AvailableSequenceNumbers collection also since it is not yet acknowledged.
• For resource-constrained servers with limited queue sizes, DataChange notifications may be purged and if so then they will only be legal if the amount of time it has spent in the queue is a minimum of 2x the number of supported Publish calls per Session – as mandated by the supported Profile(s).
For all tests (unless stated otherwise) the assumptions are:
1. All MonitoredItems are configured as follows: QueueSize=1, SamplingInterval=-1, filter=null, MonitoringMode=reporting.
2. All MonitoredItems are static and writable, meaning that their values do not change unless changed by the UACTT.

In the above test case, I am not sure about what is "AvailableSequenceNumbers", where to check? Kindly clarify.