That reflects eight weeks. When issuing permanent amendments (PA's), which this example effectively is, being dated as such, this is the agreed format as has been the case for more years than I remember. It is based around long established 'legalities' involving train crew establishment/rostering.
If the same format is followed going forward, the next CWN when issued will likely apply from Sun 20/7 to Sat 13/9.
Depending on the speed of the 701 rollout, it may be that that figure of 14 permanent diagrams rolls over as is, in to the next issue. On the other hand if things go better/faster, then the number of such diagrams will be increased. Whilst I have no inside knowledge whatsoever, with past experience I am minded to think (hope) the latter will be the case.
But looking on the down side (just for a moment), if things do not work out so well in the next few weeks, the opportunity will be there to just re-date the present CWN, complete with its 14 x 701 diagrams, and re issue same to run until 13/9 to allow reality on the ground to catch up.
I am sure this will be a work in progress as we speak, and issuing the CWN in this way for as long as the rollout takes, should have the benefit of reducing some of the workload on those other planners (and others) who will no doubt be busy enough with regular engineering work streams etc. That's my best guess.