A colonial era deed in what’s now the United States indicated that your ancestor was the grantee on a deed where he was listed as the assignee as someone else. The probable situation is that that “someone else” initially had rights to obtain that property and that “someone else” sold those rights and/or transferred those rights to your ancestor and then your ancestor obtained the property.
Here’s the but: if you are looking at a transcription of the deed with this phrasing in it, get an original image of the document so that you can see it completely for yourself. Read the whole thing and transcribe the whole thing.
And if it doesn’t make sense: ask someone about it. Look up the meaning of words you don’t know. Maybe even ask a second person.
Transcriptions sometimes abbreviate assignee as “assn” or even as “ass.” That last one is a word you don’t want to misinterpret <grin>.