I took a quick look at the sutta.
Here is the relevant verse:
” bimbisāro ahaṁ, bhagavā; bimbisāro ahaṁ, sugatāti. Idaṁ sattamaṁ kho ahaṁ, bhante, vessavaṇassa mahārājassa sahabyataṁ upapajjāmi, so tato cuto manussarājā bhavituṁ pahomi. Variant: manussarājā bhavituṁ pahomi so ito cuto manussesu rājā bhavituṁ pahomi”
I would translate that as:
“I am Bimbisara, Bhagavā; I am Bimbisara. I will be born 7 times in the company of the Great King Vessavaṇa where I am now. After passing away from here, I will be able to become a king of humans 7 times.”
So, it seems to me that he had not even gone through the 7 births in the Deva realm at the time he stated that.
– He expects to attain the Sakadagami stage during one of those 14 lives.