The grouping is done by taking all YAC's within some range into a cluster. This range is 20 by default. It can be changed with the menu entry Set Cluster Range . This lets you define a pattern. Click with the left mouse.
Pools can contain collections of clone probes and subpools.
The hybridisation pattern for a pool is the union of the patterns for all its clones and subpools, together with any data attached specifically to itself. Hitting the return key corresponds to clicking on the current active box. If you select POLY1 again after choosing this option then you get a new window, rather than reusing this one. You can then load a new pattern and compare it to the one stored in the surround. If you print when stretched out you get an index sheet for the filter like the one sent out with it.