[ortusdux]

I had to guess without albedo data, but an H of 19.2 puts it in the 0.4 to 0.5 km range, so 400m could be on the conservative side. If it randomly has an albedo of 0.05, it could be as large as 0.96km

https://cneos.jpl.nasa.gov/tools/ast_size_est.html