1090 and 978 simultaneously?

That is only part of the information. Complete information is:

(1) Leading zeros are not required.
(2) Total number of digits need not be 8 (may be less).
(3) Alphabets (or a mixture of number and alphabets) instead of numbers can be used.

That said, the 8-digit format with leading zeros is used to conform to manufacturer’s provided 8-digit counter and numbering format.