Cpt-opt-f1-ms-student-internship

Hello I am a bit confused with you CPT, OPT clarification.

I understand that if one uses 12 months of CPT. then they are not eligible for OPT.

But if that 12 months also calculated as cumulative of CPT months split between 2 masters ?

In 2015 when I was doing my MS. I used 7 months of CPT and pursuing MBA at current.

so will the 12 month CPT eligibility be reset to start from beginning or does it count as 8th month ?

look forward for your response.
thank you.