Assuming your encoding scheme means that all the characters to the right of the 'T' character should be treated as a Decimal Number, then you can use the Expression:

@(Pega-RULES:String).toDecimal( @(Pega-RULES:String).substring(.StartAlpha, 1) )

For instance, I have setup a simple Data Model consisting of 'StartAlpha', 'EndAlpha' which contains your example Text values, and 'StartNumeric' and 'EndNumeric' to hold the transformed Decimal values.

Then you can use a Data Transform (for instance) to perform the mapping:

Running this Data Transform with your example inputs gives:

<pagedata>
    <EndNumeric>9.09</EndNumeric>
    <pxObjClass>Gcs-GCSAppli-Work</pxObjClass>
    <StartNumeric>9.00</StartNumeric>
    <StartAlpha>T09.00</StartAlpha>
    <EndAlpha>T09.09</EndAlpha>
    <pzStatus>valid</pzStatus>
</pagedata>

So you should now be able to use 'StartNumeric' and 'EndNumeric' values in your Range Criteria in a Decision Table (although I didn't try that).

Note: you probably want to put in guard into your logic to ensure your input meets the specified criteria; so you might want to make use of some of the other functions available in the String (etc) library - for instance 'isDouble'.

You could build 'When' steps into your Data Transform to do this for instance.

And lastly - I have used 'hardcoded' two Page Properties in the example above (I'm repeating the same code for each 'Set') , but you might instead want to create a re-usable general Parameter-based DT transform here - that you can re-use the same logic for each of your inputs.

Cheers

John