When a 50% match isn't a 50% match?

Forum: CAT Tools Technical Help
Topic: When a 50% match isn't a 50% match?
Poster: Chris S

I did a rare CAT job today and noticed this:

Segment in TM:
Hvis der udtages biologisk materiale til en forskningsbiobank:

Segment to be translated:
Samtykke til at udtage og opbevare biologisk materiale i forbindelse med forsøget (en forskningsbiobank)

This came up as a 50% match.

Since when do four words out of 14 make a 50% match?

On the other hand, those four words do make up 50% of the segment in the TM. Is that what is happening? Is that normal?!