Sealed in their foreheads

Unless those days were cut short, no flesh would be saved; but on account of the chosen ones those days will be cut short.—Matt. 24:22.

Looking forward to the great tribulation (Matt. 24:21) What does the apostle John means with  “‘Do not harm the earth or the sea or the trees, until after we have sealed the slaves of our God in their foreheads.’”—Rev. 7:1-3.

Paul Leonard of JWquestions-and_answers gives as reply: Some of the 144,000 are chosen but not yet sealed, or they have not all yet been chosen.

What is your opinion? Or your answer?