The GED uses a scale of 100-200, with 150 being the minimum passing score. A 520 is well above passing, suggesting a decent level of understanding in the tested subject areas.
However, colleges and universities often have higher admission requirements. Some may accept a passing GED score, while others may prefer higher scores or require additional testing. Therefore, while 520 is a good score for simply passing the GED, its "goodness" relative to your future plans is context-dependent.