[求助]请大家帮我解释一段简短的语句

private: System::Void On_MouseDown(System::Object * sender, System::Windows::Forms::MouseEventArgs * e)
{
double sc=1.0;
if (e->Button == MouseButtons::Left)sc=0.9;
if (e->Button==MouseButtons::Right)sc=1.1;
System::Drawing::Size size=this->Size;
if (sc !=1.0)
{
this->Size=System::Drawing::Size(size.Width* sc,size.Height* sc);

}
}
本人是初学， 运行时出现错误 warning C4244: “参数” : 从“double”转换到“int”，可能丢失数据
不知道怎么回事。还有System::Drawing::Size size=this->Size; 什么意思。谢谢！