My Citi card comes with a desktop app that can generate new numbers for online payments all the time. Beyond one-time use, I can generate a number that will wor

My Citi card comes with a desktop app that can generate new numbers for online payments all the time. Beyond one-time use, I can generate a number that will work only with ‘x’ company for ‘x’ number of months. When I saw that, I assumed Citi+MasterCard must have at least 10,000s of times more numbers than customers