MultiLeader have different properties than standard dimensions.
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MultiLeader Format 
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Overall Scale: Sets the overall scale for the multileader.
Annotative: Set whether the multileader is annotative or not. This has no effect within the application is strictly a setting to support external DWG applications.
Arrowhead: Sets the type of arrowhead used in the multileader.
Size: Sets the size of the leader arrowheads.
Leader Type: Sets whether the type is a line, spline, or none.
Color: Sets the color for the leaders.
Line Type: Sets the line type for the leaders.
Line Width: Sets the line width for the leaders.
Landing: Sets whether there will be a landing, a horizontal line attaching the end of leaders to the content.
Landing Distance: Sets the landing width.
Content Type: This is controlled by the Style
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MultiLeader ContentThe feature of the MultiLeader Properties Content page vary depending upon the content type specified in the selected MultiLeader Style. If the Content Type in the style is set to none the page will be blank. If the Content Type is set to text the page will be as follows: 
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Text Style: Set which Text style from the Style manager is used in the multileader.
Height: Sets the height of the text. This will override the settings in the styles.
Frame around text: specifies whether a box will be drawn around the text of the multileader.
Width: Sets the width of the paragraph.
Background Mask: Creates a mask for objects behind the text.
Color: Sets the text color.
Justify: Specifies the text justification.
Left Attachment: Specifies the vertical position where the leaders on the left side of the content.
Right Attachment: Specifies the vertical position where the leaders on the right side of the content.
Text Rotation: Specifies the angle of the content text.
Landing Gap: Specifies the distance between the end of the landing and the content.
Style: Select At Least to automatically set the line size relative to the largest character of a line. Select Exactly to keep all lines the same size.
Factor: Sets the distance between lines.
If the Content Type in the style is set to block the Content page will look as follows:
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Block Source: Specifies the block to be used in the content.
Block Attachment: Specifies whether the block will be attached to the multileader using its geometric center of the block, or attached using the block reference point (insertion point).
Block Color: Sets the block color.
Block Rotation: specifies the angle for the rotation of the block insertion.
Scale X: Sets a scaling factor for the block along its X axis.
Scale Y: Sets a scaling factor for the block along its Y axis.
Scale Z: Sets a scaling factor for the block along its Z axis.