Quota gauge show warning, despite no warning level has been set

Several users (not all) have a orange or red bar in the quotagauge in their lotus notes client. This is even though no warning level has been set for these users. One user has a 2.1GB quota with zero in warning level. He has 851 MB in his box and it is orange and shows a warning, when rolling over it.Is the only way to get over this, to set the warning level to something or is there another way?