No offense but common sense does not exist in that statement.
Let me get this straight, you went to the parts store and bought a filter and gasket to change the fluid.
The 19 year old idiot behind the counter told you it takes 10.4 qts to fill it.
You drain 7-7.5 quarts out of the transmission when you change the filter.
Then you added 10.5 quarts.
And finally you posted and asked why would it be pouring fluid out of the front of the transmission?
If I was told to add 10.4 quarts, and I only drained 7, I would definitely consult another source or worse case scenario, only add back the same amount I drained out, then I would definitely check the fluid level immediately after starting the truck to see if it was close.
This may be a bit harsh, but, get some common sense!