Why can you only check one race?

<p>My racial identity is comlicated to say the least. Culturally I considered myself half Spanish (as in from spain) I speak spanish at home and am involved with the spanish cultural in los angeles, celebrate hispanic tradition. However, I am blonde blue eyed. This is further complicated by my family tree. My great-grandmother (dutch) was a baby when her entire family was killed in a raid. She, the only survivng party, was given to a spanish settlement in new mexico where she was rasied as spanish and married a spanish man. From there, some of my realitves married within the culture some did not. I have never thought about my race in a percentages and wouldnt even know how to figure it out, but some people claim that you must be this much of a certain background to mark it down. I have always checked multi-racial, but GT asks for just one. I feel like i wouldnt be doing my family justice that way. i know that Spain often is considered white im just a little bit confused
Input would be helpful. i dont want people thinking I am abusing the system by pulling out some random family member, bc really thats not it. I identify with that part of me as does my mother, but if i was asked to prove it through like some magical number i am not sure if i could bc it gets so confusing</p>