I often hear JWs say they are 'in the truth' what do they mean by this?

Only the Lord Jesus is the way, the TRUTH and the life. They cannot possibly be in this ONE because of the way they lower Him and make Him a common ' god', and not acknowledge Him as the Fullness of the Godhead bodily, or the One in whom all the Fullness was pleased to dwell. Are they in the Truth? Do they even know HOW to be in the Truth? Hardly. They do not even know what it means to " be in Christ'