One of the Weather Van boosts provides ’50% increase in County Fair and Boat Delivery Ribbons’. This boost does not include any Farmhand Ribbon Boosts.

For example, if the Ice Cream is worth 55 Ribbons and your Farmhand Boost provides +5 Ribbons, you should see a total value of +60 Ribbons for your Ice Cream item and may expect a 50% boost to provide you with +30 Ribbons for a total of 90 Ribbons. When activating the boost, the additional +5 is not taken into account however, so you will receive 88 Ribbons (the game will automatically round up to the nearest even number.)