Anchors for text boxes are highly configurable so the anchor position will always control the page the text box will be on but you will need to look at the position settings to get an idea of whether the text box is told to sit relative to the paragraph, page, margin, column etc.

If you click the border of the text box and then right click and choose 'More Layout Options' it will open a dialog where you can examine the various positioning options for the text box.

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Andrew Lockton
Chrysalis Design, Melbourne Australia