Whenever something adds a base number to a value, it's before % modifiers. This applies to tax, trade value, manpower, everything!
You barracks adds 250 manpower which also gets the benefits of +50% for grand army, for example. The top level production buildings gives +5 tax which may become 7.5 tax if you have war taxes and so on.
You barracks adds 250 manpower which also gets the benefits of +50% for grand army, for example. The top level production buildings gives +5 tax which may become 7.5 tax if you have war taxes and so on.