20*15mg=300mg
https://www.google.com.au/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=mg%20to%20ounces
1mg=0.0000335274 oz
$${\mathtt{0.000\: \!035\: \!274}}{\mathtt{\,\times\,}}{\mathtt{300}} = {\mathtt{0.010\: \!582\: \!2}}$$ ounces
20*15mg=300mg
https://www.google.com.au/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=mg%20to%20ounces
1mg=0.0000335274 oz
$${\mathtt{0.000\: \!035\: \!274}}{\mathtt{\,\times\,}}{\mathtt{300}} = {\mathtt{0.010\: \!582\: \!2}}$$ ounces