If hired by Stripe, can you estimate what portion of your day will involve coding and other activities you will perform when not coding?

The interviewer is seeking to understand how you go about doing your job on a day-to-day basis. Operational questions will ask you about the processes you use to accomplish the tasks required by this position. The best way to answer operational questions is directly and briefly. The Stripe interviewer will ask you a follow-up question if they need more information or want to explore the topic in more detail.