Original sentence: For example, the urban district Regensburg has more citizens than the rural district Regensburg, so the city has two letters after the code R.It depends on the number of registered cars (or citizens) whether the City or the district has two letters, because there are more possibilities with two letters, so the part with more citizens usually has two letters.Where this happens, the number of the following letters is usually different
Edited sentence: However, these different systems are being used in less cases as many cities that share their code with the surrounding rural districts start using all codes for both districts without any system, for example the city of Regensburg and the surrounding rural district Regensburg have used different systems only before 2007.Where this happens, the number of the following letters and digits is usually different