I do a lot of non-book cataloguing and wanted to share the following cheat sheet.
Subfields $n and $p precede subfield $h:
$a Title proper. $n Part number, $p Part title $h [GMD] : $bother title information
Subfield $n data follows a period (.).
Subfield $p data follows a period (.) when it is preceded by subfield $a, $b or another subfield $p. Subfield $p data follows a comma (,) when it follows subfield $n.
n.n If there are two subfield $n and are being displayed concurrently, they are separated by a period (.)
p.p. If there are two subfield $p and are being displayed concurrently, they are separated by a period (.)
n,p If a subfield $p follows a $n subfield it is preceded by a comma (,)
p.n If a subfield $n follows a $p subfield it is preceded by a period (.)
Do not omit initial articles from the title of a part or section recorded in subfield $p.
If a part title transcribed in subfield $p is distinctive and meaningful, record it also in a variant title field 246.
Initial articles are omitted from tag 246. The second indicator value of tag 246 is 0 for a portion of the title.
Example:
245 14 0 $a The phonics basic skills workbook. $n Part 1, $pReading readiness$h [videorecording] : $b preparing for kindergarten.
246 30 0 $a Reading readiness$h [videorecording] : $b preparing for kindergarten