The production of the planes is not a fixed schedule. If you click on the frame number on this list
https://aibfamily.flights/production-list/A350, you will see that some planes spend about 1 month from spotted in primer till delivery, while others spend 3-6 months. The normal production time from the plan reaching station 50 till delivery is 2-3 months as far as I know. The average time in station 59 is about 1 month or less.
Station 59 is where the parts arrive, and where the galley, crew resting space, toilets and other larger parts are installed.
Station 50 is the first station after station 59 and here the 3 main parts are jointed together.
Station 40 is the next station where the wings, tail, floors, landing gear, engine pylons etc. are installed
Station 30 is where seats are installed, and where all the flight electronics are tested.
Station 18 is where all the final testing before flight tests happens. This include final test of electronics, cabin pressurization etc.
Station 20 is where the final airline customization take place. This include cockpit customization and flight entertainment systems etc.
Between station 40 and delivery the plane has to be painted. Primer are always applied before the first flight, but the last layers of paint can be applied at anytime between primer and delivery.
Test flying can happen anytime after station 18 and not all planes has the same number of test flights. Most have 2 or 3, but in the list there are planes with only 1 test flight and some with 4 or more
That said. I did write that August delivery will be depending on a normal uninterrupted production. But I would not be surprised if SK has traded a delay in the delivery of A320's for an earlier delivery of the first A350. They haven't received a A320 since December 10, and they still have about 40 on order to be delivered before 2025 and currently there are around 5 in the production list with parts just starting to arrive for the first one.