A German Business Visa’s validity is determined by the embassy that issued it. The embassy can grant you a business visa with either of the following validity
Single entry –allows you to visit Germany only once and stay for the duration of your visa, which is usually 10 days.
Multiple entries – allows you to visit Germany more than once in a specified time, i.e., from January to May, with the requirement that you do not exceed the maximum number of days allowed, i.e., 20 days