C# FilesystemRights using System.Security.AccessControl

I wrote a program which retrieves all rights for a specific folder / file using System.Security.AccessControl. For all possible file I get the following information:

- AccessControlType
- FileSystemRights
- Trustee
- IsInherited
- Inheritanceflags
- Propagationflags

Here's a possible Output:
      <ace>
        <trustee>Power Users</trustee>
        <access>Allow</access>
        <rights>ReadAndExecute, Synchronize</rights>
        <inherited>True</inherited>
        <inheritanceflags>None</inheritanceflags>
        <propagationflags>None</propagationflags>
      </ace>
      <ace>
        <trustee>Power Users</trustee>
        <access>Allow</access>
        <rights>-1610612736</rights>
        <inherited>True</inherited>
        <inheritanceflags>ContainerInherit, ObjectInherit</inheritanceflags>
        <propagationflags>InheritOnly</propagationflags>
      </ace>
      <ace>
        <trustee>Power Users</trustee>
        <access>Allow</access>
        <rights>Modify, Synchronize</rights>
        <inherited>True</inherited>
        <inheritanceflags>None</inheritanceflags>
        <propagationflags>None</propagationflags>
      </ace>
      <ace>
        <trustee>Power Users</trustee>
        <access>Allow</access>
        <rights>-536805376</rights>
        <inherited>True</inherited>
        <inheritanceflags>ContainerInherit</inheritanceflags>
        <propagationflags>InheritOnly</propagationflags>
      </ace>

Can anyone explain why the rights are sometimes numbers and sometimes words. And how do I convert either the number to words or the words to numbers?