I have tested the scenario using latest release of Aspose.Pdf for .NET 10.1.0 and I am able to reproduce the same problem that incorrect page number is being displayed for TOC entries. For the sake of correction, I have logged it in our issue tracking system as PDFNEWNET-38278. We will investigate this issue in details and will keep you updated on the status of a correction.
We apologize for your inconvenience.
PS, BTW, I have also observed incorrect page number for TOC entries in result9.6.0.pdf file.