Which contentdb will my Site Collection be created in?

Let me begin by explaining the scenario…

You are in the process of creating a new Site Collection, and you expect this Site Collection to house around 50GB of data. You want to make sure that a content database does NOT grow past the recommended 100GB. The first place you head off to check is your existing content database status (current size and the number of current sites in the database).


Assume you have the following content databases:
Name DB Status | Current Number of Sites | Site Level Warning | Max Sites
SITES_WSS_1 Started 50 45 50
SITES_WSS_2 Started 50 45 50
SITES_WSS_3 Started 50 45 50
SITES_WSS_4 Started 35 45 50
SITES_WSS_5 Started 34 45 50

SITES_WSS_1, SITES_WSS_2, SITES_WSS_3 have all reached their current maximum growth, however- SITES_WSS_4, and SITES_WSS_5 both have room. So if we were to create a new Site Collection right now, where would it be created? SITES_WSS_5.

The reason it will be created in SITES_WSS_5 isn't because it has the least amount of current sites, but it has the MOST AVAILABLE. To determine which has the "most available" SharePoint takes the difference between the "Site Level Warning Setting", and the "Current Number of Sites"

Example:
SITES_WSS_4 has 10 spots available (45-35=10).
SITES_WSS_5 has 11 spots available(45-34=11).