What does the content in whatsapp web message's data-id's mean?

I'm trying to understand what exactly is the content of the data-id inside the <tabindex> on the whatsapp web messages/notifications.

<div tabindex="0" class="_2wUmf V-zSs focusable-list-item" data-id="false_55xxxxxxxxxx2-1635363427@g.us_3A0955D4295AF8A379C9_55xxxxxxxxxx6@c.us">

As you can see, I figured that the censored bits are phone numbers. I also figured that true means that it's comming from me and false if it's someone else's message. Next there is a time stamp, the @g.us means that it's group message... But I can't find anywhere what does that big hash means. It keeps changing on every message, so it's not a user id. If it's not a whatsapp secret thing, can someone tell me what it is?