How to identify follower data with ids just as tweets have unique id?


i am developing a crawler in which i will fetch that the seed user is followed by whom?
but because of API limitation only 5000 users will be returned in one api i don’t know how i will identify that first 5000 followers ? so that i can fetch next 5000 with the help of this identification?
the followers have ids but they would be random not sequential as in case of tweets???

any help will be appreciated! it’s urgent