Considerations for Multiple Notifications in the Same Transaction | Streaming API Developer Guide

Streaming API Notifications Sent in Reverse Order Within a Transaction
In general, event notifications are delivered in the order of record changes. One exception is that when a record triggers multiple notifications within the same transaction, the last notifications are delivered first.

Multiple Streaming API Notifications for the Same Record
In API version 37.0 and later, if a field change triggers other field changes on the same record, more notifications are sent for those fields even if they aren't tracked. Also, if a field changes multiple times in a record during a transaction, multiple notifications are sometimes sent. The notifications are sent regardless of whether the field values match the PushTopic query.

Only Last PushTopic Notification Sent for the Same Record
In API version 36.0 and earlier, when multiple PushTopic notifications are generated for the same record within about one millisecond and in the same transaction, only the last notification is sent.