2.82 Python Slider min and max

Hello. Python beginner here. I have been trying hard to set the min and max values of my slider with this FloatProperty. In vain.
What is wrong ?
Thanks in advance for your help.

>         main_bone = bpy.data.objects['Armature'].pose.bones["Main"]
>         row = layout.row()
>         bpy.types.main_bone.scale[0] = bpy.props.FloatProperty(min=0.5, max=1.5)
>         row.prop(main_bone, 'scale', index=0, text='Height')
>         row.prop(main_bone, 'scale', index=1, text='Width') 
>         row.prop(main_bone, 'scale', index=2, text='Depth')`