One-time passwords are so called because of their generation algorithm. In addition to the private key, the one-time password counter is also used here. Each time the password will differ from the previous one. The counters on both sides must be synchronized: if at least one password is missed, they will not be the same and the algorithm will be broken. Another convenient option for one-time password generation can be synchronization by time. In this case, the generation algorithm does not use the counter, but the current time. With time synchronization between the devices, you always get the same passwords on both sides. According to RFC 6238 standards, the time is rounded up to the nearest 30 seconds: for example, every 30 seconds your one-time password will change.