In summary:

• Use previous event time – each time you add a new diary event it will use the same time of day as the most recent event of that type. For example – Tue 07:00 Breakfast, then on Wed adding a new breakfast event will default to 07:00. 
• Ask to share – when adding new foods/items you will be prompted to share the item with the community. This prompt can be turned off here (or when prompted).
• Always share items – stops prompting as above, and simply shares any new items with the community.
• Share usage data – this provides us (the developers) useful information about how people use the app – the screens most used, and how people move around the app. This helps us understand if there are any bottlenecks or problems so that we can improve the app. No personal information is shared. 

Kind regards,
mySymptoms team.