[Решено] Correct hreflang code

Background of the issue:
I am trying to understand the correct hreflang code for my website. I noticed discrepancies between the settings and the source code. The page in question is скрытая ссылка. In the source code, I see: . However, in the settings, the default locale is pl_PL and hreflang is pl-PL. I expected to see the correct format as per ISO 639-1 and ISO 3166-1 Alpha-2 standards: . Screenshots are available at: скрытая ссылка and скрытая ссылка.

Symptoms:
The hreflang code in the source code is 'pl-pl', which does not match the expected 'pl-PL' as per the settings.

Questions:
Why is the hreflang code 'pl-pl' in the source code instead of 'pl-PL'?
How can I ensure the hreflang code matches the settings?