Trade Bug - I'm not even sure i should be opening this thread here

Fractional values will be rounded to the nearest half to prevent undercutting by unrealistic amounts.

If you want to use more precise values, you can use the ratio format as described here.

So for 0.6 chaos, you'd list your fusings as ~b/o 3/5 chaos (selling your 5 fusings for their 3 chaos).