Updating an existing point?

Documentation says:
“If a write would overwrite a point in a prior TSM file, the points are merged at query runtime and the newer write takes precedence”
How is newer calculated here, both points are exactly same and in different TSM files. Does the query runtime also gets this information about what TSM file the point came from and TSM files creation time is measured. OR each point also contain an insertion time apart from timestamp?