Each item are made to order. These are approximate times it means that it’s not 100% guaranteed. Sometimes it can take longer than expected. I always do my best to get closer to the indicated time, but sometimes due to a late restocking, or other logistical problem, it may take longer.
The deadlines are not cumulative, if you take 2 minimap, that does not mean that it will take 10 weeks to do them. For very large orders, I would attach a personal message to indicate an approximate time between taking charge of the order and sending it