Can someone explain this in details please? i dont understand? i wuld appreciate it !?

A computer will individually number all entries received from each region. After the end of the registration period, a computer will randomly select entries from among all the entries received for each geographic region. Within each region, the first entry randomly selected will be the first case registered, the second entry selected the second registration, etc. All entries received during the registration period will have an equal chance of being selected within each region