IBU calc with higher than anticipated gravity

I did a pumpkin batch over the weekend. My calculated OG was 1.049 not counting the pumpkin addition. I expected to hit 1.053. Evidently I had great efficiency or got alot of sugar out of my pumpkin (I did use a ****load of pumpkin) as I ended up at 1.062.

My calculated IBUs were originally 31. My OG is off by around 20%. Would my IBUS at 1.062 be 20% less at 25 IBUs?

I know IBUs are subjective and all that, just worried this is going to taste like a box of pumpkin flavored nerds.

Using BeerSmith and just plugging in 60 min hops until I get 25 IBUs at 1.053. when changing gravity to 1.062 it drops to 21.9 IBUs. So no, not a 20% decrease, only 8.76%.