I'm reading a children's book (this one) and I found this expression in a dialogue. The dictionaries don't help me much to understand the meaning, which I suppose is ironic, but I'm not sure.
Here's the context. A boy and a girl are training a pony:
‘He needs to go slower, I think!’ Ellie called. ‘It says here [on a horse-training manual]: “the horse should settle into a steady trot”. Can you slow Solo down while keeping him going round the outside?’ ‘I think so.’ Joe moved so he was level with the pony’s neck. Solo instantly bounced to a stop. With a snort, he turned and raced in the other direction at an even faster canter than before. Ellie giggled. ‘Think again!’
Is the meaning of the exclamation ironic? Can someone formulate the sentence differently to help me understand?