Seems you were outsniped - your 300 went in between the snipe by p***r and the end of the auction - a gap of about 7 seconds. Ebay correctly rejected it as not being at least one increment above the highest bid.
Now, if your snipe had arrived sooner AND p***r had only bid 300 then you would have won. If he'd bid 300.01 then you would have lost!
Next time bid higher and add a few pence/cents so that you might win in a draw...
R2