"Days in column" dots explanation

I'm trying to work out the logic behind the Days in Column dots on JIRA boards but can't quite get it right.

It's almost the following:

1. A grey dot is 1 day
2. An orange dot is 2 days
3. A red dot is 3 days
4. Only show dots for up to 12 days

But those rules don't work for a handful of cases.

Here's my data, taken from a snapshot of one of my boards:

https://docs.google.com/spreadsheets/d/16oGvpQomtJEaS6hmhNfFaDub-4nafmi1jJ32PYMSyvQ/edit?usp=sharing

Does anyone know the logic behind this?

See the "Using Days in column" on the online help:

Blank dot → 1 day
Grey dot → 2 days
Yellow dot → 3 days
1 red dot → 5 days
2 red dots → 8 days
3 red dots → 12 days
4 red dots → 20 or more days

Note that if you move an issue back to a column where it's previously been, the indicator gives you the cumulative number of days the issue has stayed in that column.

The logic has also changed recently according to this post stating "the new dots behaviour is available only in Cloud".

There is an outstanding bug where the weekends are counted as days. This might explain why your data doesn't align.