Stuck in a simple GSCE Question

The question as given (to my brother) was the following
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Every cream pastry contains 430calories. If I walk briskly I will loose 5calories/minute. After eating 's' cream pastries and then walking briskly for 't' minutes, the calories 'c' which I would have consumed are given by:
c = 430s – 6t
(c=calories s=number of cream pastries t=number of minutes)

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By nature I assumed that there was a problem in the equation and it should have been
c=430s - 5t

Since you multiply 430 by the number of cream pastries you have eaten

and then subtract by 5*t (as you will loose 5 calories * number of minutes)

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I consulted with my lecturer which however denied that there is a mistake in the problem. Does anyone know any possible reason ?

Thanks a lot for any help.

You are correct. Did you point out the discrepancy to your lecturer or generally ask if there was a mistake in the communication of the problem/answer?

When I (my brother) pointed what I meant , he said there was a trick and that it was correct. Now I'm assuming that he just tried to cover it up.. but according to my Alevel knowledge, there is no possible reason. Thanks for sharing your view :)

yes, it looks right to me too 430s - 5t