DataSnap Auth - please tell me Here or via Skype (for $$). Dual authorization and sessions - how?

Question

Delphi

Prompt please:
There is a DS (HTTP/REST) ​​server. There is a mobile client (DSRest).
Before executing the method (requests via FireDAC/JSON), the client is authorized on the server.
I just can't figure out why the onAuthenticate event occurs twice on the server, the first time with an empty login/password, the second time with real data.
Those. in the logs I see
Authentic.1. user:
Auth.1. pass:
Authentic.2. user: vasa
Authentic.2. pass: farcry
TFDStringList
Auth.3. user:
Authentic.3. pass:
Authentic.4. user: 111111
Auth.4. pass: 3423423
If it is possible to get a Skype consultation, I will gladly pay based on the rate of $10/$20 per hour.