"Tawat'at" linguistically means to step or walk on, that is, to place foot over the place where one's fellow kept his foot. Here, it is used in the sense of correspondence. In other words, "I see that your dreams all agree upon the last seven nights" stands to mean "you had similar dreams". This was done by showing all of them the (spectacle) of Lailat-ul-Qadr. On the strength of these dreams, the Prophet (PBUH) said that Lailat-ul-Qadr should be sought in the last seven nights of Ramadan. The wisdom of keeping it secret is to keep people awake to engage in worship for a larger number of nights in this auspicious month.