Fee math is easier when the percentage and fixed component are separated. WMIX lists a standard fee of 5% + 0.0007 BTC. For example, on 0.01 BTC the stated service-fee components total 0.0012 BTC; on 0.1 BTC they total 0.0057 BTC; on 1 BTC they total 0.0507 BTC. The useful question is not how...