Some juices cannot be sealed in barrels if they are in amounts with a non-whole number of (0.01 L) increments. For example, you can seal 4.1 L of blackberry juice, but not 4.11 L, even though the recipe is one-to-one. But it is not consistent, as you can seal 4.11 L of black currant juice. In the guide, the recipe points out that 10 mL of black currant juice turns into 10 mL of black currant wine. The same entry for blackberry juice says that 0.1 L turns into 0.1 L of wine. Which is why you can't an extra 0.01 L in the container.
This is very confusing and makes no sense, most people would just assume you can't make that wine unless they dug around in the help pages and figured out why the math doesn't add up. You will almost always end up with barrels of non-round numbers of liters, since the conversion from stacks of berries to juice goes from powers of 2 to multiples of 10.