Buffs like the 200% oil boost granted from subscriptions do not show a direct correlation between time reduction and increased production.
The way that this works is that it increases the ratio of how many resources are earned per second, reducing the time that it takes for the pump to fill.
EXAMPLE:
As an example let's say an Oil Pump generates 1 unit of oil per second and a storage that has 100 capacity total.
In this example, it will take 100 seconds to fill up the storage of 100 units.
For this same example, if the Oil production is increased by 25%, this will generate 1.25 units of oil per second. This will then take 80 seconds to fill up that same storage, or a 20% decrease in time to fill, if the storage is empty.