Why isn't my integer value processed correctly with PHP in Rules?
I was able to solve this problem after finding the answer on my question 'How to use variables in a PHP evaluation in a rule?'.

Instead of activating the Rule when an event "After saving a new field collection item" occured, rather use "After updating existing content" and grant the Userpoints for the first Field Collection item in a different Rule. Afterwards, follow the instructions in the referenced answer and use the code underneath.

&lt;?php
if ($old_total &gt; 5) {return 0;}
elseif ($new_total &gt; 5) {return 5 - $old_total;}
elseif ($new_total == $old_total) {return 0;}
else {return $new_total;}
?&gt;