Obscure definition for "amount"

If you had 5 apples, the amount of apples you would have is five. Or it could be used plural to sum up the total potential to something/someone. "Phil is going to amount to absolutely nothing" basically its just the sum, or total of something. Its not used often because it feels kind of unnatural in normal conversations. More commonly you will hear things like "How much money do you have" and they are basically asking for the amount.

Selected examples from the ever-reliable OED:

†3. The full value, effect, significance, or importance of something. Obsolete.

1678 J. Flavel Divine Conduct 129 There are divers things to be distinctly pondered..before you can judge the amount and worth of it.

1726 J. Thomson Winter 9 Ye lying Vanities of Life!.. Where are you now? and what is your Amount?

1845 J. Lingard Hist. & Antiq. Anglo-Saxon Church (ed. 3) II. App. g. 397 What the real amount of that statement may be.

1881 Times 24 Dec. 5/3 The amount of it is that you have too much to say in this case.

As the definition says, this use is obsolete; I'm surprised that neither dictionary you linked marked it as such. (I've personally never encountered it--perhaps that's because I'm an American and Collins says it's more of a British thing.) Anyway, Oxford's examples are straightforward enough. If you've got institutional access to the OED, you can look at the full entry: oed.com/view/Entry/6575.

Here are some definitions from wordigg Amount A*mount", v. i. [imp. & p. p. Amounted; p. pr. & vb. n. Amounting.] [OF. amonter to increase, advance, ascend, fr. amont (equiv. to L. ad montem to the mountain) upward, F. amont up the river. See Mount, n.]

1. To go up; to ascend. [Obs.]

2. To rise or reach by an accumulation of particular sums or quantities; to come (to) in the aggregate or whole; -- with to or unto.

3. To rise, reach, or extend in effect, substance, or influence; to be equivalent; to come practically (to); as, the testimony amounts to very little.

Amount A*mount", v. t.

To signify; to amount to. [Obs.]

Amount A*mount", n.

1. The sum total of two or more sums or quantities; the aggregate; the whole quantity; a totality; as, the amount of 7 and 9 is 16; the amount of a bill; the amount of this year's revenue.

2. The effect, substance, value, significance, or result; the sum; as, the amount of the testimony is this. source : https://wordigg.com/amount-definition