Currently the data type for attribute 19.168 draw:extrusion-specularity[1] is zeroToHundredPercent. In ODF 1.1 it has been percent. The data type has been changed in OFFICE-2509 [2].

The current data type is not suitable:
The extrusion of custom shapes has been designed strongly following RTF, VML and MS Office binary formats. The corresponding attribute there is c3DSpecularAmt. MS Office uses it with value 80000/65536 ≈ 122% in many shapes created in the UI and OpenOffice.org 2 had written it with 122% in ODF 1.1.

A higher value than 100% is meaningful, because the value is used as factor in a product with light intensity. Light intensity has usually values between about 58% and 80%. So to get a bright light spot you need a value for extrusion-specularity which is higher than 100%.

My proposal is to allow values larger than 100%.

Such could be done by changing data type back to percent. We could add, that the value must be non-negative.

To make it not-negative we could add the restriction in the text or introduce a data type nonNegativePercent and use that.
Such would be
<rng:define name="nonNegativePercent">
  <rng:data type="percent">
    <rng:param name="minInclusive">0%</rng:param>
  </rng:data>
</rng:define>

[1] https://docs.oasis-open.org/office/OpenDocument/v1.3/os/part3-schema/OpenDocument-v1.3-os-part3-schema.html#attribute-draw_extrusion-specularity
[2] https://issues.oasis-open.org/browse/OFFICE-2509