In fact this verse (NO. 284) is the continuation of the last phrase of the preceding verse that: To Allah belongs all that is in the heavens and in the earth. Therefore if you reveal or conceal that which is in your mind, it makes no difference for Him. He knows all, and will call you to account for it. Then He will forgive whoever He will, if He knows him deserving forgiveness, and He will punish whom He pleases for his sins. Then don't you ever think that, deeds such as concealing evidences and hiding testimony will escape His knowledge or sight.