[defrost]

Did you read your linked paper?

Figure 6. does not show total Antartica ice mass change, it shows a local area change in relative sea level markers.

Today the relative sea level markers are much lower as the land itself is riding higher overall due to glacial rebound, the lifting of the land as a great weight is removed.

Your paper (as discussed in the conclusion) argues that during the past 6,000 years a great deal of ice has been lost, having retreated some 30km and thinned by some 800m in thickness.

Did you make a typo, or did you misunderstand your own linked source material?

Either way, thank you for the paper.