Hi, my name is Wrinks! My son recently enquired about his National Insurance contributions

My 51 year old son recently enquired about his National Insurance contributions and was advised that sometime in the late 1990/2000 there appeared to be a deficit of approximately 
£250 … my query is ,, I am led to believe that to receive a full pension when reaching that age you must have contributed for 35 years , he will retire hopefully when he is 67 meaning that he will have exceeded the 35 years as stated above , should he pay the shortfall , will he lose out monetary wise if he doesn’t