Second time a charm.

I already held a PDX-EWR award booking on UA which cost 12,500 SQ miles that got schedule changed by 1+h. I used this opportunity to change the aforementioned flight to PDX-JFK on AS. At first, the rep wanted to charge me the US$30 fee as he said there is an airport change. I replied that this is my only alternative due to the schedule change and usually change fee would be waived in this circumstance. At my request, he spoke to his supervisor who agreed to waive the fee but I had to forfeit the 500 miles difference (AS Zone 1 PDX- Zone 4 NY should have only cost 12,000 SQ miles). As it's not a big amount, I said "ok lah, that's fine".

Are miles usually forfeited in this case?