The closest approach '.008 AU' to Earth is on May 22, 2013.
Nevertheless, .008 AU is still about three times the distance of the Moon - Earth, or about 744,000 miles, but it is remarkable that Asteroid 2013 KB sits around the same position for almost 1 day before moving on.
Listen to the information and explanation from OutrDemnDarkness in the video below:
Besides, there are two additional asteroids coming in along with 2013 KB:
1. 2013 KTI at 3.2 lunar distances with closest approach on May 21st, condition code 5
2. 2013 KS1 at 4.8 lunar distances, closest approach on May 22nd, condition code 8.