The instruction was for a finished size of 4 x 2 (4-1/2 x 2-1/2 raw size). You need to do a little math to find the other dimensions:
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For a 5 x 2-1/2" flying geese unit (5-1/2 x 3 raw size):
take the long dimension and square it (i.e. 5-1/2 squared would be 30-1/4)
divide that in half (15-1/8)
take the square root of that (4 when you round up)
add seam allowance to give you a 4-1/2" strip for the geese and a 5-1/4" strip for the sky (always 3/4" larger).
So your Step 3 strips would be 4-1/2" wide
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I haven't tested this though - let me know if it works for you!