Explanation:
If {} is blank - it means that there is something which shouldn't be there in your original text; if there is something between {} - it means that there was something wrong in your text and I have changed it or have added something more to the text.
Cat found
Cat wearing {a} blue collar found in the park about 15th April. Cat is black and has got a small white spot {on} the tail, very friendly. Cat {feels} good and {is} waiting for {its} owner. Please {dial on} [tel].