Experimentally, how did they measure the amount of ejected electrons ?

Typically you just measure the current produced by the ejected electrons, which is an indication of how many electrons were released. The area over which the ejected electrons come from is irrelevant.

Did they simply divided the total number of ejected electrons by the area

That would give a number of electrons ejected per area, so that isn't a number of electrons.

This answer was for version 1 of the question.

Experimentally, how did they measure the amount of ejected electrons ?

Typically you just measure the current produced by the ejected electrons, which is an indication of how many electrons were released. The area over which the ejected electrons come from is irrelevant.

Did they simply divided the total number of ejected electrons by the area

That would give a number of electrons ejected per area, so that isn't a number of electrons.

Experimentally, how did they measure the amount of ejected electrons ?

Typically you just measure the current produced by the ejected electrons, which is an indication of how many electrons were released.

Did they simply divided the total number of ejected electrons by the area

That would give a number of electrons ejected per area, so that isn't a number of electrons.

Experimentally, how did they measure the amount of ejected electrons ?

Typically you just measure the current produced by the ejected electrons, which is an indication of how many electrons were released. The area over which the ejected electrons come from is irrelevant.

Did they simply divided the total number of ejected electrons by the area

That would give a number of electrons ejected per area, so that isn't a number of electrons.