I'm not using an S4, pero noong nakuha ko yung unit ko selyado naman ito. Sa harapan ko pa binuksan yung box at nagdemo ng unit. Gumamit pa nga ng ballpen yung CSR para hatiin yung selyo sa box ng unit.
(Experience ko lang po ito ha, I'm not saying na ganito lagi.)
They are usually sealed by Globe when they deliver to their outlets.
Some people from tthe outlets (or GBC) open it for test purposes and to check if the IMEI would correspond to the box and unit.
Just check the unit yourself too as you have 7 days to return it aside from a a one year warranty.
If by a chance you are not satisfied with your unit and decide to return it, ask for a sealed unit if it would make you feel better..