True.
Big rear sprocket = better acceleration, lower top speed.
Small rear sprocket = better top speed. lower acceleration.
However;
There is a price to pay because if you mess with the sprockets you affect the gearing so riding up hills or with a head wind will be more difficult. Only consider doing this is you ride mainly in top at near the top end of your bikes speed. With a DT I wouldn't change the gearing. If you do intend to, minus one tooth would be enough. There is a spreadsheet to calculate what the changes would be in Excel. You should be able to find it with a little googling - motorcycle gearing worksheet or LINKY for an online one.