Stanley returns to digging, seething about how unfair not being rewarded for his fossil is. Soon, he notices X-Ray watching him. X-Ray asks to talk and explains that he's been at Camp Green Lake a year, but he's found nothing. He admits his eyesight is poor and explains that his nickname doesn't have to do with his sight; it's just his real name, Rex, in pig Latin. X-Ray asks Stanley to give him anything interesting that he finds, as he's more deserving of a day off. Stanley agrees. As Stanley resumes digging, he thinks he made the right choice: it's more important for X-Ray, the group leader, to like him than it is to get a day off.
When Stanley recognizes that it's important to cozy up to X-Ray, even if it means never getting a day off, it shows that he recognizes that the social structure among the boys at Camp Green Lake is based on low-key bullying and intimidation, not necessarily camaraderie. This trickles down from the way that the adults treat the boys; the boys are learning by example that intimidation and cruelty are the only ways to gain power over their lives.
Stanley marvels that X-Ray is the leader, since he's the smallest aside from Zero. Stanley thinks that Armpit is the biggest before realizing that he himself is actually bigger. He thinks he likes his nickname, as it means the group has accepted him. Stanley thinks of how scared Derrick Dunne would be of any of the boys here, and imagines his new "friends" standing up for him against Derrick. It eases Stanley's pain to know that in his mind, Derrick is suffering worse.
Stanley's realization that he's the biggest suggests that he may be coming to terms with the fact that if he chooses to take it, he may have more power than he gives himself credit for. This implies that he's beginning to understand the way that the social structure works at camp, and that possibly, he's becoming less kind.