Odoo14

When I create Manufacturing order (mrp.production) sometimes  I get extra moves (extra line in move_raw_ids) and I don't know  why they get created nor what do they represent.

I've found out that it always derps out if my  product  lines "To consume" & "Consumed" are  less  than  1  and  unit of measure is unit (always gets extra move line and sometimes gets auto filled values that are 100x than original lines),  I assume unit shouldn't be less than 1 but if that's the case it shouldn't let me enter it (it just happened that I was testing with small values.)

Anyway that isn't the problem, problem is that in my  company sometimes the actual consumed value "Consumed" can be smaller than planned  consumption value "To consume"

So when I do the above case when I want click "Mark as done" I get "You consumed a different quantity than expected for the following products. Please confirm it has been done on purpose. " and I confirm,  but  then  I get extra move lines that are auto created which have values of  0/0 for "To consume" & "Consumed" , what are those?!?

I've tried to look it up into docs or Google but did no find explanation.

I've also been looking at and debugging the core code but the code is all over the place.

To recreate my case is:

new Manufacturing order with 10 quantity to produce and 2 product lines:
first product has "To consume"=4 and "Consumed"=3.85

second product has "To consume"=6 and "Consumed"=6

When I click Mark as done button and confirm the warning I get these lines:

first product has "To consume"=3.85 and "Consumed"=3.85

second product has "To consume"=6 and "Consumed"=6

third product is same as first product but with "To consume"=0 and "Consumed"=0

Notice how "To consume"  changed  after  marking  it  as  done  on  first  product,  that  is  not  that  big  of  a  problem now (I found in code where I can fix that for my needs) but I don't understand what is the third,  empty,  product supposed to represent?