When she came to him, she urged him to ask her father for a field. And she got off her donkey, and Caleb said to her, “What do you want?” She said to him, “Give me a blessing. Since you have given me the land of the Negeb, give me also springs of water.” And he gave her the upper springs and the lower springs.
Joshua 15:18-19

More extensive negotiations between Caleb and Othniel are hinted at in v18, but skipped over. It begins with Achsah urging her new husband to ask her father for land and ends with the land already having been given.

Clearly Caleb cared about his daughter very much. She asked for an additional blessing from her father so that she could take full advantage of what he had already given her, and he gave her twice as much as she asked.