The calculated distance (air line) between Giv'at Shmuel and Ashdod is approximately 23 miles respectively 37 kilometers.
By car or train, the actual journey to Ashdod is certainly longer, as only the direct route (as the crow flies) between Giv'at Shmuel and Ashdod has been calculated here.
Air line (approximately)
37 kilometers
20 nautical miles