Yo

I have a question which I could work out the answer to easily however I am not sure which of two figures I should use. Would be grateful if someone could advise me on the correct one!

Gross Domestic Product (GDP) is currently at 100 units growing at 3.5%

In 8.5 years what is the value of GDP

Now obviously I know the formula is

Y=100e^0.035*t

However I am unsure on whether it should be as of whole years so therefore using t as 8 or using t as 8.5?

Any suggestions?