Since you have Office 365. Provided that you have the latest update applied...

=SUM(LOOKUP(SEQUENCE(C10,,1,1),A4:A8,C4:C8))

If you need it to be compatible with older versions...
=SUM(LOOKUP(ROW(A1:INDEX(A:A,C10)),A4:A8,C4:C8))

Confirmed as array (CTRL + SHIFT + ENTER).