Did you weigh it? 60 grams is like 2 jumbo Mice and it sounds the way you explained it that its much bigger than that. At 300 grams you should feed around 40 grams.
I had a bad experience once with a Rat that was to big for a 550 gram Ball Python. I was use to feeding my burm so all the Rats looked small to me and she (what I call) choked on it... she tried to get it back out of her mouth when she couldn't make it past the Hips/Back legs... i'll never make that mistake again. Scared the hell out of me. A correctly labeled Small Rat is to big for any 300 gram snake IMO
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