How is “device_id” generated - Vkontakte API?

Question

API

Started learning VK API. I began to send requests, to understand what and where. There were no special problems except for the "device_id" parameter. I did not find an answer on the VK API documentation page.
First, the question is appearance. When catching requests, I found that VK's POST request eats it in the following form "device_id: 0.8258351440131606". The value changes every time and, obviously, is not tied to the device itself.
I thought maybe it was just a GUID, but it looks completely different.