transport belt madness run resets available items

[abnessor]

I don't known, it's bug or not.
But i don't remember this behavior earlier.

At first try some years ago, i difficult to complete some missions by simple belts excess and need exchange some belts with underground.
Toady i found, when start level and go back, available items reset to initial.

[Klonan]

You get infinite items anyway

[Bazinga]

Abnessor, I confirm the behavior. If you start with 50 undergrounds, place all, Start the run, Go Back to building, you get another 50.

"You get infinite items anyway" - Klonan, what is meant by that?
If player startet with 50 undergrounds and used 50, no more can be placed unless player goes to "Start the run" - so how is this infinitife anyway?

[Klonan]

Abnessor, I confirm the behavior. If you start with 50 undergrounds, place all, Start the run, Go Back to building, you get another 50.

"You get infinite items anyway" - Klonan, what is meant by that?
If player startet with 50 undergrounds and used 50, no more can be placed unless player goes to "Start the run" - so how is this infinitife anyway?

The crafting menu allows you to create additional items at no cost.

The scenario is not about using limited items.