Hi Aditya ,

In response to your question that whether all the subject marks are merged or only one subject marks are given in the NIOS board marksheet if we appear for only one subject then I must tell you that if you appear for only one subject it will show only one subject's mark and you have to use that marksheet along with your regular marksheet which will contain all the other subjects mark to apply for any specific college,  position or wherever you want.