I read on the website that they recalculate your benefit every year. If you have another year of contribution that exceeds a past year, then it can up your benefit. Keep in mind that their calculations include dollar normalization from past years to present years, so you may want to look at it in terms of did you have a max contribution year that will replace a 1/2 max contribution year.
Example:
My MIL has a short history, only been working for 15 years. She plans to work till 70, but will begin her benefits this year at 62. She will receive the reduced benefits due to her income now (-1 for every 2 in salary over $13000), but that reduction will be added back when she does fully retire. Also, every year she works till 70 replaces a 0 earnings year, so it will continue to make her benefits grow each year when they recalculate. Her yearly contributions are like 1/5 of max, so the recalculation doesn't put much more into her monthly benefit, but at least it is something.