Text box script

In addition to the good advice given above, you need to add an extra pair of parentheses to the if-condition, like this:

if ((section == "3A" || section == "3E" || section == "3J" || section == "3T" || section == "3Y" || section == "3Y" || section == "5B" || section == "5C" || section == "5D" || section == "5E" || section == "5G" || section == "5H" || section == "5I" || section == "25") && gravesite > 0)

First, you should remove the quotes around the 0's (eg. gravesite > "0").  The quotes turn a number into a string.  It works in this case because the JavaScript engine will interpret it as a number but doing this might give problems in a different context when using a number comparative.  Calculation scripts run every time any field value changes so a calculated field will always revert to the calculated value after a user enters a value in the field.  If you want to avoid this and allow users to change to value, you can use a validation script in the IntermentSection field instead.  You can use the same script but change this.getField("IntermentSection") to event, and change event to this.getField("[the name of the field]").  Here's a reference for Calculation vs. Validation scripts:

https://pdfautomationstation.substack.com/p/calculation-vs-validation-scripts

Another method is to put restrictions on your script so it only calculates if the values of the fields in the calculation change:

https://pdfautomationstation.substack.com/p/another-method-for-calculation-vs