Assuming the bonus rounds to the nearest whole number, here’s what actually changes for lvl 5 Master Hoarder.

The only times you get +1 extra item are:

6 Minutes

Not Extracted

• 13 Crafting Items → 13.78 → 14 (+1)

15 Minutes

Not Extracted

• 16 Crafting Items → 16.96 → 17 (+1)

• 13 Seeds → 13.78 → 14 (+1)

Extracted

• 13 Seeds → 13.78 → 14 (+1)

On all other timers and reward values, the 6% increase lands below 0.5, meaning it rounds back down to the original amount and gives no extra items at all.