What happened here?

Question as I am new to masonry, was working on cleaning the brush when I saw a thin cut up to the windowsill of my washroom.

My home was built in 1991 and my foundation has had repairs done in the last 10 years. Looks like a concrete saw cut a straight line up to the window sill then was filled by an epoxy but just wanted to get a second opinion.

Thanks in advance.