I finally got my hands to experiment the factories and they have some weird performance issues or missing instructions.
If I make 1 product line for jewellery and put 2 parallel laser cutters with each having their own input station, the production line displays that it produce 1 item in 30 minutes and 1.67 items / hour, BUT if I decide to use only 1 input station and splitter, my production speed drops to 0.83 / hour.
The laser cutter takes 1 hour to produce 1 item, or 2 paraller to produce 1 in every 30 mins so these numbers dont make any sense.
Also, if i use 2 input stations, 1 for each production lines the production shows 1.67 / hour, but i use splitter and connect 1 metal band input to 2 parallel production lines, 1 continues as 1.67 but other changes to 0.00