Device associated with another apple ID

I bought and 2nd hand phone which was factory reset.

I have been using it for over a year. I have purchased new content no problem.

when i want to access content i bought on my ipad it says my phone is associated with another apple id Transfer or cancel

What does Transfer mean...transfer what to what...

I have searched and found no clear answer..i have seen posts which state restricted for 90 days after which ok but i have had the phone over a year and the 90 days does not get any shorter

Should i have selected transfer? but without knowing what i am transferring?

for clarity i only have 1 apple id...so i assume the other apple id would be the previous owners

any clarification please