does "up to" mean that it's ok to only get 6mbps when I pay for "up to 300mbps"???

I've occasionally run into not being able to open a basic webpage and started running tests. Today I've ranged from 6-39 mbps down and 3-44 mbps up. I don't need much, 200/200 Ziply was more than enough for me before, is this normal? Can I do anything? Shouldn't there be a minimum speed?