learning curve

Kiss Co has developed a new product. The first batch of 200 units will take 3,500 labour hours to produce. There will be a 75% learning curve that will continue until 4,800 units have been produced. Batches after this level will each take the same amount of time as the 24th batch. The batch size will always be 200 units. Note: The learning index for a 75% learning curve is -0.415.

what is the time taken for the 24th batch (to the nearest hour)?
answer : 552 hours

my answer 545 hours

i understand how to do this question, but i dont understand at which decimal point should i take, the answer stated that

total time for 24 batch is (24*936) = 22464
total time for 23 batch is (23*952.7) = 21912.1

the way i did for the 23 batch is (23*953) as the question stated that it wants it in the nearest hour, so i assume that i need to round it up in the calculation and the final answer also and i got a different answer than the scheme