Hi,

 a quick start guide in the following link; hopefully this will help.

Good luck

 file:///C:/Users/Aamal/Downloads/Vector_NTI_Advance_11_Quick_Start_Guide.pdf

The real ORF must start with an appropriate start codon, be relatively long and must end with an in-frame stop codon.

Dear Vicente, 

All ORFs in the software start with start codon and end with stop codon, this is not the point, I think. 

(Relatively Long), this is the point, can you tell me, what is the minimum length for example?

Thanks for your answer. 

The variation is very wide.  Try to google "shortest protein" or "shortest polypeptide" as well as "longest protein".   Alternatively, you can google "shortest ORF" and "longest ORF".  HTH.   BTW I said "in-frame stop codon" and not just any other stop codon.   

Ok. Thank you very much.