multiply a byte * 256 then add a byte in a dbc?

working on an xml can description for real dash and also working towards a man in the middle device for the bmw pt can to send syvecs friends can sensor data to use as many factory sensors as possible such as lat g, steering angle, ambient temp etc.

heres an examlpe of some already decoded can signals

https://www.loopybunny.co.uk/CarPC/can/0AA.html

Can-ID

Length

DATA Packet HEX

DATA Packet DECIMAL

Register Desctiprion

0AA

8

5F 59 FF 00 34 0D 80 99

095 089 255 000 052 013 128 153

Byte 4 & 5 = RPM

Engine RPM

Hex 0D34 = 3380

3380/ 4 = 845 RPM

EXCEL / Arduino Forlmula = ((Byte[5] * 256) + Byte[4] ) / 4

Example Above = (( 13*256 ) + 52 ) / 4 = 845 RPM

the byte format is intel hex but i have searched high and low to figure out how to add this to a dbc and came up empty handed.

any help or links that explain how to accomplish this would be epic!

also are there any tricks to figuring out how to decode such messages. i have a list pulled from a tool32 .prg file with all the major can ids and descriptions that will leave alot less needles in the haystack once all those are figured out

i can't read the text as it's really light blue on a white background.