On first occurrence of a value on a spot in array-message as well as on a first array-message from a source observable processed by deepMap, function provided to deepMap is run. First occurrence in a spot, as well as every other change happening under a particular index in every other consecutive array-message will trigger a new message being sent through provided observable and will not run the function that first received it. Detail-observable is a stateful observable meaning, on every new subscription it'll immediately reemit last message.