CentOS - Apr 2015 - mirrors still catching up and -01.iso images?

I'm watching a couple of mirrors catch up with the 7.1 release and am
noticing some churn on the .iso images.

It appears that new -01.iso versions are coming downstream while some
of the mirrors apparently were getting different .iso images.  The
-01.iso versions look to be significantly larger than the previous
non-01.iso versions (the -Minimal .iso appears to have gone from 560M
to 630M for -01.iso).

I'm not downloading the larger .iso image so don't know the actual
content, but the md5/sha files also changed and some of the mirrored
-01.iso versions appear to have different sizes (actually from the
timestamps it looks like the non-01.iso versions might have been
renamed -01.iso before being replaced with newer content).

What is the difference between the non-01.iso versions and the -01.iso
versions?  Is this what we can expect with the monthly rebuilds?

For tracability reasons, I don't like seeing different .iso images at
different times.  We really need to see consistent content on the
distribution mirrors.

Some of this may still be churn and one mirror may have run out of
disk space (or otherwise be waiting for manual intervention).

Stuart
-- 
I've never been lost; I was once bewildered for three days, but never lost!
                                        --  Daniel Boone

I now see an announcement on the centos-announce list which explains
most/all of what I was seeing last night.

Stuart
-- 
I've never been lost; I was once bewildered for three days, but never lost!
                                        --  Daniel Boone