Weird SSRS Format Date Output in Matrix report Header

For one of my Matrix reports, the column headers are Dates which I am trying to format in the form of 'Mon 07' i.e. short date name followed by date value.

For this I am using the expression - =Format(CDate(Fields!WorkedOnDate.Value),"ddd") I then wanted to trim the right 3 letters.

I am getting weird output. Here is what I am getting for one week- Tue, We2, T12u,ri,SaA,Sun,7on

Any idea what is going wrong? This was asked in this link but that answer didn't help - The date formats do not seem to work in SSRS

Regards,
Karthik

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