Sometimes you will sell your client a certain number of hours without really defining which services will be included in the work. However, you still want your people to start tracking time somewhere. In Productive, we call this Open hours.
Open hours will appear in your budget only if you have created a project from scratch, without defining financials/services in advance in your sales deal.
Open hours exist so that your people can start tracking time on a project without the need of defining specific services to track time against.
Later, when you know exactly which services your people have worked on, you can redistribute Open hours to those services.