Billing document number range

Hello experts,

I have created a new number range for existing billing document types based on sales org and plant. In development it worked fine but in Production the first 3 invoices got the number range 00001, 00002, 00003 but fourth invoice jumped to 00100. After that no other invoice was created but I checked in table and current no. is 00199. I have not maintained any buffer. I can understand nos. jumping by 1 or 2 but 97 is a lot. Any idea why this is happening?

Regards,

Karan