When doing compression tests, the important point is not the reading of all
the cylinders, but any major variance between them which would indicate a
problem with one or more cylinders.

Cranking pressures can vary by a considerable margin compared to "factory"
specs depending on things like the equipment used during the test, how you
actually do it and the temperature of the engine at the time. Suffice to
say, if your engine was running fine before it blew a head gasket I wouldn't
be concerned by low readings.

--
Regards,
Noddy.