Yes. You are right. I have just checked the page right now, and found that 06 types of engine oils for passenger cars are being offered right now by Caltex / Havoline: 0w-20, 5w-40, 10w-30, 20w-50 and CNG 20w-50, 10w-40. Link is:
https://www.caltex.com/content/caltex/pk/en/motorists/havoline-cars/passenger-car-motor-oils.html
(The last two appeared after clicking on "Show More Products" and I did not know about it, that's why I previously thought that 10w-40 is not offered here. Thanks for the correction and clarification. 
)
Yes. There are differences between 10w-30 Vs 10w-40, major being Kinematic Viscosity figures at 40°C and at 100°C.
ZIC 10w-40 is fully synthetic and meets API SN criteria (which is current and latest), whereas caltex 10w-40 is mineral based, and meets old API SL criteria.
If you have not, then I would suggest to return it, and go for Total Quartz 9000 Future Series 5w-30 instead. Try this first, and then move to 10w-30, and later 10w-40.
If inclined towards 10w-40, then go for ZIC instead.
