Circuit Training and Weights

Hello. I have been adding circuit training to my routine this last week and had a question. I am using the set up at my local Planet Fitness so they have everything set up with the stations. When I am at the weight lifting stations how heavy should I have the weights? Are they supposed to be only heavy enough that I can lift the entire time I am at the station? Or do I make them heavy enough where I do 10 reps have to take a break and then do 10 more? They have a light there that lets you know when to switch stations so its not self paced. Just trying to get the most out of my routine.

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