The thing is it doesn't say "working on your current permit for 1 year" but the original question is "Have you been
working full-time for the employer on their current work permit
for at least one year" and so if you have been working for them in past (for example from 2010-2015), you have been working for them at least one year then.
Also here
http://www.cic.gc.ca/english/immigrate/skilled/exempt.asp it says:
"For Express Entry, your employer doesn’t need an LMIA if you have been working full-time for the employer on your work permit for at least one year" and so if the company you've been working for is the same company as stated on your work permit, then you have been working for them. It doesn't need to be
on this specific work permit.
I'm not native english speaker though, as you can probably see.