Your planned hours are shown in My planning in your personal menu. Here you can view and edit them for each week, and add personal time-off like holidays.
Tapping a project will open the deliverables and activities you are planned on. Tapping on the activity or on personal time off will open a window where you can edit the hours for that week. Changing you planned hours will send a notification to the manager of the project, so he or she can check it.
Planned hours will show in your timesheet, so if you stick to the planning, you can directly submit these hours for approval. Otherwise you can correct them before submitting.
Your regular working hours for each week are set under 'Employees' in the back office. VOGSY will indicate over-planned hours in red.