From your screen shots, both samples have the number starting half a centimeter or so in from the left hand side so I would think that is consistent.

The tab space after the 7.4 sample but not visible in the 7.5 sample could imply that there is also a tab after the 7.5 but the following text is hiding it because a default tab stop was reached (and 4 is fractionally wider than 5). We would need to see the ruler in your screenshots (or preferably your actual document) to be sure what is causing the space to collapse.

Read the references that Charles has provided and you will get a better understanding on what is going on with your document.

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Andrew Lockton
Chrysalis Design, Melbourne Australia