what was a bit strange for me because locally checking (ie. from system preferences -> iCloud), they take about half of that size:
Then I looked up into other positions on the list and saw Messages take the rest of the 2GB I saw firstly:
It is strange for me, because as you can see in first image, there is no such position as Messages on the bar, only bigger Backup position. Then I deleted all the messages on my iPhone to see if anything changes, but it did not change anything in the size of messages shown in system preferences. I do not know if it is some kind of error, or messages will disappear from iCloud later.