Did I do my Port Mapping Correctly on my Time Capsule?

Hi,

Basicly I have a LaCie network space MAX and I want to access it outside of my network. I did it, I can access it outside of my network but, I don't think I did it correctly, I think I lowered my homes internet security. I attached an image of showing how I configured it:

As you can see I made everything 21, since I am connecting to the drive wirh FTP but, I don't think I should make everything 21 as it will lower my network security.

I am asking what I shou;d keep 21 and what I should keep blanl.

My other question is I have another one of these LaCie network space MAC and I want to access the VIA FTP as well but my router will not let me make the port 21 since I already used the drive as 21 is there a way to make both work on port 21 or is there another port for FTP I can use.

Thanks for your help!