Source
It’s from this DOJ publication:
https://www.bjs.gov/content/pub/pdf/rhovo1215.pdf
They don’t lead with the breakdown, but in Table 1, you can work out who victimized whom at what rate.
For the number of black-on-white crimes, multiply total white victims 3,679,410 by the percent of black offenders 14.7% = 540,873 b-on-w crimes.
Doing the same with w on b: 850,720 x 10.9% = 92,728 w-on-b crimes.
The total number of b/w interracial violent crimes then is 540,873 + 92,728 = 633,602. Black on white share of this is 540k/633k = 85%