As far as the Saath Bhathan is concerned, it means that there are seven layers of meaning to the Holy Quran, and they are continuous layers. That is to say, if you start from one point of view, reading and understanding the Holy Quran, you can continue till the end, and the thread will never be broken. If you just, like a kaleidoscope, change your angle of vision, and enter another thread of meaning, that would also be continuous, and although the words are the same, new meanings would appear to every word, and this will continue to be carried on and on by other words, following verses and so on, and they would not end even with the surahs, new surahs would take up the kajal from where they left, and like a medley race, they will go on and on.
So seven bhathun means different layers of meanings, but it does not mean seven. Seven is a figure used by the Arabs to show perfection, and seven could mean seven plus many many more. You can say, when Arabs apply seven, seven is the minimum. For less than seven, this figure cannot be applied, but it does not end at seven. It may mean much more. So now coming to the second part of your question, when Hazrat Khalifatul Masih II commented on this, he took it to be the minimum seven, and from that he inferred that the Holy Quran has prophecies and predictions about all the huge changes which were to occur in the world, philosophies and attitudes and learnings and so on, great events. Not events, but eras in fact.
So he conceived that there would be seven eras of learning for the mankind from the time of the Prophet, till the end of time, that is the doomsday. And all these have been mentioned in the Holy Quran, and bhathun also means secret. So he is looking at the word bhathun in that respect, not as layers of meanings, but meaning that there are seven great secrets contained in the Holy Quran, which apply to seven different eras of learning and achievements by human beings. And they have been mentioned and we are passing through one era, but that could not be the end of it, another era laid on upon mankind, which again will be mentioned in the Holy Quran. Nothing would be new to mankind.
