what is the minimum download speed !!!BASED ON MY PLAN!!!

I fully understand that speeds can vary due to type of modem, Internet traffic, yada yada yada.   My question has nothing to do with the actual service to my home.   Please keep this in mind as you respond. Thank you ahead of time, saving us all time and trouble.

I would like to know what is the MINIMUM guaranteed download speed of my service, at the point of the modem.   I have Blast Pro+ and, according to my bill which I can view online, I can get speeds up to 400mbps.   But that is the MAXIMUM speed.   I would like to know what the minimum speed Xfinity/Comcast provides for my service.   More importantly, why is this not prominently displayed anywhere on the system?   Minimum AND maximum download AND upload speeds should be provided.

Again, please, save us the dread of explaining that it depends on many factors.  We already know this.  What I am asking simply is:  What speed range am I supposed to be getting for Blast PRO+ and not get into the details of exactly what hardware configuration is present.   I am talking ONLY about the contracted speeds for these plans.   Exactly what did you sell me?

Thanks for a clear and concise answer that does not reiterate what we already know as is so common with technical support.