What does "/ws/XbeeCore" "xpUpdateTime" response element really mean?

On the Digi Remote Manager Programming Guide, p.286, I find:

Time the node was last discovered.

But I don’t know what that really means, or in other words, what does that time really tell. Can a node be “discovered” several times so that it would be necessary to know when was the last time it was discovered? I thought the node was discovered only once on the very first time it joined a network. Or is it talking about the time a node was last “connected”?

Could please someone help me understand what does “xpUpdateTime” really tell?

Components … Doesn’t restore any reactions from a send_message direction. … The burden to utilizing the XML design is that it is verbose. … The off choice implies that Remote Manager will regard the push occasion as … GET/ws/XbeeCore?condition=xpExtAddr=‘00:13:A2:00:00:00:00:00’&cache=false …

I don’t really understand what you mean. I’m sending the command as:

curl -X GET https://user:pass@remotemanager.digi.com/ws/XbeeCore?condition=devConnectwareId='00000000-00000000-000000FF-FF000000'