Incorrectly marked as Unauthorised Absence

[SaveMeNow2024]

Both my kids were off school for 1 day in January due to illness. I contacted the school to let them know both of them would not be attending that day.
I recently noticed that my eldest child had 2 unauthorised absences (morning & afternoon), while my youngest didn't have any. I queried it, and they said I hadn't informed them about my eldest. I sent a screenshot of the text I sent.
They then said that they are not able to amend the mark as more than 5 days had passed.
AIBU to expect them to change the mark to Authorised?

Does it really matter?

Absolutely does matter and I'd be pushing for the change/contact the local authority if the school won't do it.

What difference does it make?

In what way will it matter to the child and family?

It really doesn’t matter

When schools bang on about attendance so much, and take punitive measures against the transgressors, it absolutely does matter that they record it accurately.
I had this at DDs school more than once. I take attendance seriously. I contacted them each time it happened and asked for it to be changed. As I didn't get their record until the end of each term, I wouldn't have been able to ask for it within a timeframe, but in any case they did indeed change it.
If it isn't important, don't record it. If it is important, record it accurately

Of course it matters, this is your child’s personal data and it’s inaccurate. Make a right to rectification request to the school; if there’s sufficient evidence to validate the request then legally they cannot refuse.

ICO | Right to Rectification

It's a legal requirement for schools to accurately record attendance. I understand that mistakes happen, but they should rectify them.
Otherwise what's the point of recording attendance?

Under gdpr laws they must correct any inaccurate information that they hold about your child. The system wont let me is not a valid excuse