I think this is a misinterpretation of the document. The claim is:

> 70% of ICE arrests are of criminal illegal aliens charged with or convicted of crimes in the U.S.

I believe the claim here is that 70% of the people ICE arrests have been charged with or convicted of crimes other than being present in the USA illegally. I don't think this is at all meant to imply that 30% of arrests are of people who are present in the USA legally. I think it's just sloppy writing.