browser.mailTabs.getSelectedMessages() returns 100 elements only

Hi,
I’m trying to write a Thunderbird extension that loops through all selected messages in active tab and stuck with return object from browser.mailTabs.getSelectedMessages() method. ‘messages’ array is always confined to 100 elements regardless how many emails are selected in message list.
Any idea what is the reason of behaviour?

Regards
K.

https://webextension-api.thunderbird.net/en/latest/how-to/messageLists.html

Oh. That clear… Thanks.