Inventory Time Calculation Method

Hello members,
Need your valuable inputs on inventory time calculation method. I am doing VSM current state mapping in one of the factory, during which we stuck on inventory time (between two process steps) calculation methods. i referred books, articles and found out that there are two methods – based on per day demand or based on cycle time. i checked with both the methods and i have attached screen shot. so by using per day demand (which is simple one) i got inventory time 5.6 days, but based on cycle time i got inventory time 128 mins; so these both values are differ a lot and this will impact my process efficiency calculation. from one articles, as this current state map we should use cycle time method to have realistic view. so i need your inputs if you have used these methods during your VSM sprints, which one is preferred or how both methods have different impacts.
Details of attached VSM – customer demand per day is # 7, Takt time is 52 mins & inventory qty. are collected by gemba walk on VSM sprint day.