Some nursing school admissions committees look at your prior transcripts from other schools and calculate your overall GPA. However there are those schools that only calculate your GPA based upon pre-requisite and co-requisite courses. Plus, there are schools that only want you to take courses from them so courses taken at other schools would not count. On the other hand, there are schools that count pre-requisites and co-requisites taken more then once no matter which school you have taken them from.... and so on and so on...
Basically what I am trying to say is that there is no set standard for all nursing schools. The best thing for you to do is cut down your confusion and contact the school(s) you wish to apply to and ask how GPA is calculated for admissions into their program.