molecules with "BLAH BLAH BLAH" in them

The ZINC15 database has a wonderful selection of molecules.
I found a handful of molecules with the generalized positional index "BLAH" in their names. Perhaps this is a new shorthand for denoting positions on scaffolds.

Consider the following 7-ring scaffold

It's name is 18,19-diazahexacyclo[BLAH.BLAH.BLAH.BLAH.BLAH.BLAH.BLAH]nonadeca-1(3),2(4),10-triene.

I guess moieties could be placed at any of the 7 BLAH positions on the scaffold.
Marvellous!