A bit of a deviation...
I've only just discovered this weekend that I've been using the dough calculator on this forum incorrectly. I'd been making two errors that combined to give me odd results. My two errors were to express the preferment as a percentage of the total dough weight, instead of as a % of the flour weight, and secondly I mistakenly thought that the percentage of water in the preferment was a bakers percentage... I'd been entering 100% all this time when it should have been 50%.
Somehow this hadn't ruined my pizza, but it did mean my hydration levels and starter %s have been out of whack, and unsurprisingly whenever I did manual calculations I'd get completely different results.
I only twigged when I noticed that if the starter was supposed to be 2.5% and the salt was supposed to be 2.5% then why are they different weights?? How it had gone on for this long without me realising I'm not sure... but mystery solved!