Claudius recognizes the name on the sign, Magnus, as the name of a man he'd like to meet -- a man who helped Galahad at his lowest, which makes him a more precious ally than any Claudius would cultivate for his own ends¹. And though he's no longer seeking distractions from a broken heart, Claudius enjoys learning skills for learning's sake. He dwells on the first skill, which has little enough explanation. But Claudius recalls the single handsign he agreed on with Galahad. Galahad has other wants, Claudius knows, that he struggles to voice. Even if he learns to voice them with time, Claudius has seen how distress steals Galahad's ability to speak clearly or at all. A language of signs, even a rudimentary grasp for it, would be most useful.

The trouble is, though he'd like to meet the man, Claudius hasn't the first notion of what Magnus looks like. So he memorizes the areas on the sign, and adds them to his daily circuit of the mansion, keeping an eye out for anyone he doesn't recognize.

¹ Yes, that means Shen Qingqiu is also a precious ally. Claudius isn't going to stop gossiping about him or making fun of him or looking appreciative when Lan Wangji coldly disdains him, but their alliance isn't contingent on such things, surely.