You can think of this like a checking account bonus. The 10% APY is about 4.5% over what's available nationally from a CD. If you have the full $2.5K earning this for 10 months, that'll result in about an extra $94.
The credit union's field of membership includes employees of the City of Fitchburg, Fitchburg State College, and other places. It also includes students of Fitchburg Public Schools and their family members. Becoming a member of the Friends of Fitchburg Public Library or the Friends of Coggshall Park can also qualify you for credit union membership.
The credit union only has one branch located in Fitchburg, Massachusetts which is about 40 miles west of Boston.
Fitchburg ME FCU is NCUA insured. It's a small credit union with $23.5 million in assets and just over 3,000 members.