If you use NiceLabel counter, NiceLabel sends data to the printer separately for each label which increases the amount of data sent to the printer and slows down printing.
If your thermal printer supports the internal counter (most of them do), define the printer counter on your labels. Printer counters reduce the amount of data transferred between your computer and printer and speeds up the printing.
By default, the printer counter is enabled in NiceLabel. In case you made some changes follow the steps to enable printer counter:
Start NiceLabel Designer.
Go to Variables and select Counter.
Double click your Counter variable to open Counter properties window.
On General tab in Printer Counter section select Use printer counter if supported.
Important: The printer counter works only if you use also the printer's internal fonts. When you place a text object on your label that you connect with your counter variable, select printer font.