'On the table are three cups and four plates' was rejected, but we don't really need to say 'there' are in this construction.
I completely agree.
Every time they have a construction like this, Duo rejects it if you don't include the word "there", which is really annoying since the "there" is entirely optional in English and is more often than not omitted.
Still not fixed. Reported again: 24/06/2018
Dish was marked incorrect for тарелка?
Yes, тарелка means "plate".
what is wrong with on the table there are3 cups and 4 plates?
DL does not accept numbers in texts.