thank you for bringing this to our attention, I have logged this as a bug in our bug base.
in the mean time, you can manually modify the css to change the alignment of the Fieldset description. In the CSSFormBuilder/FD_Sharp_Default.css file, Find:
form.Sharp_Default span.fieldsetDescription {
color:#b40000;
text-align:right;
float:right;
margin-bottom:5px;
}
and change it to:
form.Sharp_Default span.fieldsetDescription {
color:#b40000;
text-align:left;
float:right;
margin-bottom:5px;
display: block;
width:100%;
}