There are many body composition machines, so it's hard to tell you if theres a problem or not. If it is just a scale that measures your body fat then there could be a margin of error. Body fat scales use a technique called Bioelectrical Impedance Analysis... or BIA for short. Very simply...
A small and completely harmless electrical current is passed through your body. The electrical current passes more quickly through fat free tissue like muscle than it does through fat or bone tissue. So...
The amount of resistance to the electrical current relates to how much fat-free mass a person has and their body density. Here's the first challenge...
Like all body fat tests, body fat scales don't actually measure your body fat percentage. They determine your body density. The examiner (or the scales) then uses a formula to calculate body fat percentage based on body density.
The problem with this is the results can change based on what you've eaten, and more likely, what you've had to drink. The more water in your muscles, the higher the body fat reading. So to start your percentage that was given to you may be flat out wrong. But the chances that your body fat % is higher because of the muscle alone is slim. Hope this helps at all!