CAN I CHANGE THE (LISTED) WALK:RUN RATIO?
Yes.
However,
My last 30 years of data were used to determine the training prescription I've specified for your program. 
This means, for most people who choose their most fitting program, the ratio's will work. Also, once again, please consider my training philosophy of DTI & time on feet allowing all fitness levels & running talent to benefit concurrently.
However, if you feel like a change either way (harder or easier) is a better fit, please consider the following feelings.
Shorten the walk phase (e.g. by 1 minute).
♣ I feel like I could repeat that session right now!
♣ I could talk easily during the entire session.
♣ It doesn't feel like I'm getting a workout.
♣ I'm not sure this coach knows what he's talking about!
Lengthen the walk phase (e.g. by 1 minute).
♣ My knees hurt.
♣ Geez, I'm hungry two hours after my session.
♣ I couldn't talk throughout the session.
♣ Boy, I was looking forward to the walk phase.