Yes, each domain has a unique tracking code.
The tracking code is in the Remindee script that you have to add in your website pages. So, please be sure that the Remindee script that you paste in your website is the one associated with it.

How to find the Remindee script associated with your website
1. Log in to your account
2. Select the domain in the Sites menu, in your Remindee header
3. Click on “Site settings > Install Remindee”, in the left side menu
4. Copy the Remindee script and paste it in your website pages