插入图片时出现奇怪的错误

Question

\begin{figure}[ht]
\floatbox%
    [{\capbeside\thisfloatsetup{capbesideposition={right,center},capbesidewidth=4cm}}]
    {%
      figure%
    }%
    [\FBwidth]
    {%
      \caption{\textbf Variation   of   average   grain   size   of   nanostructured NiFe2O4   with  milling  time.  The  continuous  line  is  guide  to the eye.}%
      \label{1fig}%
    }%
    {%
      \includegraphics[scale=0.3]{1fig.jpg}%
    }
\end{figure}

这是我的代码。我收到奇怪的错误，提示“缺少数字，视为零”。我该如何纠正？