the rule about income says that only income from periods where you have been member of an A-kasse can be counted.
But you tell you have been member for 1 year, and if you in that period have earned more than the maximum amount DKK 19,029 every month, then 1 year membership should be sufficient for you.
Then the next thing is that your income must be normal salary that is reported by your employer to the "Indkomstregister".
We can't tell why your employer maybe not have reported your income to the "Indkomstregister" correctly. You must contact your employer to ask, if there is a mistake. And I am sure they can correct it by doing a new registration in "Indkomstregisteret".
It is out of the scope for our website to say why your income is not registered correctly in the "Indkomstregister". But the A-kasse can only use what they see in the register.