Confusion about mining productivity and output rate

[bluohh]

Hello everyone.
I have this mining patch, composed of 8 big miners with 4 productivity module 2 each, with mining productivity research level 15.
Rate calculator mod shows an output of 32 stones/s.
However clearly I'm not getting that much, or the red belt would be filled up. Why is that?
I thibk that the wiki tells that there are different types of productivity, one that increases the output and another that decreases the ore depletion.
However I cannot estabilish which is which.

[Loewchen]

They stack the output.

[Khagan]

If I were you I'd ditch the productivity modules.

With no modules or productivity tech, you'd get 20/s output, with the deposit depleting at only 10/s (thanks to the big drills' inherent bonus).

With level 15 productivity tech but still no modules, you have productivity of +150%. The deposit still depletes at 10/s, but the output is 50/s.

Adding the modules increases the productivity to +174%, but also gives a -40% speed penalty, along with big increases in energy consumption and pollution. The deposit depletes at 6/s, and the output is (as shown) 32.88/s. The output per depletion has a modest increase from 5 to 5.48, but every other statistic has got much worse.

[Ranec1]

Once you unlock stack inserters from Gleba it adds a related ability to have stacked belts. It is listed in the technology.

This changes the buildings from the other planets. Recyclers and Big Miners will both spit out stacks which increases the throughput accordingly. Smaller miners stay as single.

I cannot think of anything else that it applies to as most do not dump onto a belt but require inserters. Unsure if it would automatically effect mods or not.