yes because it's a little bit complicated. in Polish language there's no the same this and that words. they are just similar, so sometimes you can use both. translating them into this or that is easier for foreigns than to learn which adjective is correct for which specific situations.
if you imagine that the sandwich is near you, then you say to jest kanapka. and if you imagine that the sandwich is far far away from you, then you say tamto to jest kanapka. you can not be always sure which suits better, because it is just a course, not a real life, right?