Greetings

I am brand new to CAD and am taking an online beginners course for Solidworks on Udemy called "Master Solidworks 3D CAD (2021)". 
I'm using 2024 version.  I've reached a lesson on Configurations and adjusting parameters of a simple drawer assembly, but am running into a problem that the course instructor doesn't seem to have. 

I made the base floor part. Then I make the back wall and the left