When deciding your most meaningful experiences, you need to think of the reason why this activity is so meaningful and the impact it has had on you and on others. It is the description that you provide which is going to matter more so than the actual hours. Of course you always want to include activities that show commitment and progression, but if you really feel this is a meaningful experience, than you should include it as such. The best thing you can do is not select meaningful experiences just based on the number of hours you put into them but reflecting on the transformative nature of the experience. You need to really reflect on how this experience has shaped you and then decide if, out of all the other amazing things you have done, this is really the most meaningful to you. If so, then make sure you craft a very strong description for it showing what you have learned because of it and mentioning how you can apply this learning moving forward. Best of luck!