Perforated pipe Installation

A perforated pipe is designed with small slots or holes to allow water to exit or enter easily. This type of pipe is frequently used for underground drainage systems and other outdoor uses due to its ability to absorb and drain water.
• Perforated pipe (PVC)
See in link for pipe connection

[@shahidkiani9170]

Aggregate Bed, and Surrounding 15 cm and 30 cm on top of pipe

[@sercandemir6073]

Please forgive my ignorance about my question but I have to ask this. As we can see in this video, there are some perforated slots on pipe surface. This means that undesired water can easily discharge from the soil. But how can we calculate the number of slots on surface and also is it necessary to create a slot on the bottom of the pipe? I mean we collect the water from the soil for discharging but because of the slot on the bottom, it is possible to transfer back this undesirable water to the soil. I hope I share my thoughts in an understanably :)