Last service is obviously not done by SC since they used BHP sticker.
Many fake sifus out there believe older cars need to use thicker oil, hence the insistence on using 5W-40. This has some truth in it when you are talking about cars from the 80s, 90s or modern Toyotas that are still using those old engines. but not modern Korean cars like the Cerato. Another reason is due to price, 40 is usually cheaper than 30, so most workshop stock them and try to push it to owners.

Anyways, it doesn't really matter much as long as the engine oil is good quality, you can change it over to 5W-30 later.