The number of entries depends on various factors: the complexity of your logo requirements, your level of interaction, and the contest time remaining. Simple, icon-based, logos will usually receive more entries. A complicated logo, such as a character illustration, takes much more time.
If you participate frequently in your contest by providing daily feedback and rankings you can expect to get a lot more entries than someone who offers no interaction during the contest. Energy creates energy. Some contests do not receive the majority of their entries until the last 2 days or less. There are many reasons why this happens. Continue a high level of interaction in your contest and be patient. If you still have concerns, visit the current Contests page - this will likely put your mind at ease. As a last resort, you can contact Support for help and suggestions.