Share based compensation stock options grants

Hello guys,

i have a doubt from stock options and grants.i came across various numerical questions which i got wrong. the cbok says the stock grants & options are both measured at fair value at the time when they r granted and expensed immediately or over the service period.my question is do i just have to look at the options granted on the grant date and its value or something else also?what about its value after the grant date?i am confused.