The reason that you are just getting the last number is because of this line...
"int score = 0"
Because of this, everytime you have a recursive call it is resetting the score to 0.
Then the function is just returning 0 + the last number
The easiest way to fix this would be to delete that line,
change "return score" to "return 0",
and change the other return statement to be
return a[counter] + Math.min(jumpIt(a, counter + 1), jumpIt(a, counter + 2));