Surprise on the dataset without rating column

[chetanambi]

Hi,

I am new to recommender systems. My dataset looks as below. The time_spent column is the duration in milliseconds the user spent on the app. The requirement is to recommend the similar top 4-5 apps to all the users. I am confused if I should consider time_spent column as the 'rating' column or not. Or is it the case of the implicit rating scenario? Appreciate inputs! Thanks!