Expand object by specified number of pixel/number of modules


Is there any limitation in terms of module numbers. I have to analyze 70 images and wanted to add two modules per image but after 111 modules I cant add any more, it stops responding. Also, I have identified nuclei as the primary object, now I want to expand the objects to get the whole cell but I am not sure about the number of pixels for expansion, could you please suggest me how do you do? I am working on human B cells in different tissues. Any help would be great.
Best regards