Yes, if you remove that activation of Studio One, you will have only 2 of 5 activations in use.
For Studio One 4 Users requesting an activation reset request, you can manage your own activations in your https://my.presonus.com account by clicking on the "My Products" link once logged into your account. Then choosing the "My Software" link. Then click the link to "View All Details" for your registered software you wish to change the activations for.
Once you have clicked on the registered software in your account, you will see the link as illustrated below:
Here you'll be able to remove activations freeing up licenses that you may need.
You do not need to contact support to do this. This is now entirely controlled by you the customer for each of your software licenses.