What does the 08 and 18 suffix callout in the Vishay part numbers BAT54A-G3-08 and BAT54A-G3-18?
The last 2 digit suffix calls out the packaging codes.
-08 calls out a 3000 piece, 7" reel (8mm tape)
-18 calls out a 10000 piece, 13" reel (8mm tape)
This information can be found on the datasheet. Click here for the Datasheet