A Level Biology Question

https://www.quora.com/profile/Bravewarrior/p-150990669
Here is the question, the solution and my working out. I got 0.05, but the correct answer is 0.06. My question is, in the exam would they allow a range of answers or would I lose a mark for this? Thanks!

When calculating initial rate using a tangent on a graph, you always draw a tangent from the first point on the graph, in this case where time = 0 mins. On the mark scheme it looks like they just take the difference between the first data point and second data point.

p.s. I would not waste time writing "initial rate = gradient = m = delta y / delta x =" as you will never get marks for it in the exam and you need that time for other questions.