***Advice Needed*** digipak CD

[Pat_Mustard]

Just looking for a bit of advice from qualified graphic designers.
A friend of mine recently hired a graphic designer for the layout of a digipak CD.
Upon completion of the layout, the graphic designer sent the files to the duplication/pressing company.
The pressing company came back with the following errors in the work:

"Booklet 12+1 - The black background layer used in indesign is - 100%
C, 100% M, 100% Y, 100% K. The black in the image on top of this does
not match this ie is - 63% C, 52% M, 51% Y, 100% K. We recommend that
when CMYK are added together the numbers should not exceed 320%.
Booklet 2+11 (as above)
Booklet 10+3 (as above)
Booklet 4+9 (is ok)
Booklet 8+5 (is ok)
Booklet 6+7 (is ok)

On the disc - Bring the black mix under 320%

A good solid black mix is - 100% K & 50% C,M & Y

Digipack has no bleed. - Ignoring the flap - artwork should measure
258mm x 293mm (inc 3mm bleed applied on all sides)

The Spot UV varnish plate needs to be 100% k ie greyscale. So that we
can generate the separations. It needs reversed so the black areas
will print and the white areas wont. the black is a CMYK mix at the
moment."

I'm just wondering, is it normal that these errors were made or does it reflect badly on the graphic designer?