field		start	length	format

header:

inv nbr		0-4	5	nnnnn		unique invoice number
contr nbr	5-9	5	nnnnn		summit contract number
contr seq nbr	10-14	5	nnnnn		number of invoices this contract
adv nbr		15-19	5	nnnnn		advt number
agc nbr		20-24	5	nnnnn		agency number
rep nbr		25-29	5	nnnnn		rep firm number
ae nbr		30-34	5	nnnnn		a/e number
inv date	35-42	8	yyyymmdd	invlice date
frm date	43-50	8	yyyymmdd	billing period from
thr date	51-58	8	yyyymmdd	billing period thru
description	59-88	30	a		user defined
inv amount	89-99	11	nnnnnnnn.nn	invoice amount
# detail lines	100-102	3	nnn

detail:

inv number	5n
line number	5n
record type	2n
contr nbr	5n
contr page	5n
spot id nbr	5n
copy nbr	5n
copy pg nbr	5n
channel		5n
run date	8d
run time	8d
amount		11n
agcy comm	11n
sales tax	11n

all of the "numbers" are record id numbers that
are used to access that particular table.
we can provide the expanded information
if desired (advt name instead of number) on any of them.