Reviews

Recently, I am asked for a minimum of 600 characters for a review, whereas there are published reviews with far less characters than that. In addition to this, I have sent reviews with less than 600 characters, have been accepted and published. Is it a new regulation please, or what. One more thing. Before finishing my review, I see written "your review cannot be accepted because it does not contain 600 characters", or something like that. What's going on please?