Numbers with Rings uses an OpenType system that allows you to generate numbers in rings up to 999999. You can even have ringed letters or letter/digit combinations. If your application supports OpenType ligatures, you can type letters or digits on your keyboard, and they’ll automatically squeeze into rings. First, select a ring which can hold the number of digits you want, then type the digits; the rest happens automatically. There’s also a filled ring which can be used to give your ring a colored background. For more details on how Numbers with Rings works, check the PDF user manual.