Thanks for your posting and using Aspose.Cells for GridWeb.
We were able to replicate this issue with your source file. GridWeb does not recognize the subscript and superscript text. We have logged this issue in our database. We will look into it and resolve this issue. Once, the issue is resolved or we have some other update for you we will let you know asap.
We have analyzed your issue a bit. Currently we don't support subscript and superscript in GridWeb. Although, the feature is a little complicated, but it can be done. We will estimate the requirement thoroughly and enhance it later on.
Once we have any update on it, we will let you know here.