Am I abusing the concept of a property settor by having the property datatype not match the data type of the corresponding field?

I have a class that represents an rtf document ClsRtfDoc.

Instantiating an ClsRtfDoc object reads an rtf file and it first parses the rtf file to obtain various rtf file metadata.

For example, I have a field int paperHeight that I use to store the rtf file paper height parsed from the string that holds the rtf file contents.

Since the rtf file content is in a string variable, the PaperHeight property data type is a string and the PaperHeight property setter parses the paper height from the string blob (e.g., look for \paperw12240\paperh15840 and grab 15840 from the blob), converts it to an integer, and sets the paperHeight field to the integer value. See code below.

I constructed the code this way because I want to isolate the parse + set operation. Am I abusing the concept of a property settor by having the property datatype not match the data type of the corresponding field? Is there a better practice (design pattern?) I should be using in constructing this code?

CODE

public partial class ClsRtfDoc
{
    int paperHeight;

    public string PaperHeight
    {
        set
        {
            MatchCollection objPaperHeight = Regex.Matches(value, "(\\\\paperw\\d+)(\\\\paperh\\d*)");

            if (objPaperHeight.Count >= 1 && objPaperHeight[0].Groups.Count == 3)
            {
                if (!(Int32.TryParse((objPaperHeight[0].Groups[2].Value).Replace("\\paperh", ""), out int paperHeightValue)))
                {
                    throw new FormatException("Can't find paper height");
                }
                else
                {
                    paperHeight = paperHeightValue;
                }
            }
            else
            {
                throw new FormatException("Can't find paper height");
            }
        }
    }

    // CTOR
    public ClsRtfDoc(string fqFRtfFileName)
    {
        string rtfTextFromFile = GetRtfFromFile(fqFRtfFileName);
        PaperHeight = rtfTextFromFile;
    }
}