There's a ton of conflicting information on the net. This is due to a combination of differing personal tastes, and genuinely different optimal ways of brewing tea using different teaware. Different companies tend to give their brewing instructions in a different way.
With time you can learn how to interpret each company's brewing instructions. For example, Upton Tea Imports, a company I like, caters distinctly towards western tastes and western brewing methods. Their brewing instructions are not suitable for gong fu brewing. However, companies that specialize in Chinese and Japanese tea often give instructions more suitable for brief steepings in a gaiwan or yixing pot. If I choose to brew these teas in a mug, or a western teapot, with a single infusion or only two infusions, I need to drastically reduce the amount of leaf and increase steeping times.
With experience you learn how to identify each source's brewing recommendations, where they are coming from, and what they mean, relative to the ways you like to brew tea.
However, if you just encounter brewing instructions and you know little to nothing about the source, and their preferences in taste and brewing, the instructions can often be as good as useless!
Experiment, and take everything you read with a grain of salt. But brewing instructions from the same source are often very useful relative to each other. I.e. if I am buying from Upton, and they say to only brew a tea 1 minute, I know that it infuses very quickly, because their default recommendation is 3 minutes, or if they say to brew it 5 minutes, I know it infuses more slowly than normal. I can then adjust that if I'm brewing the tea to my own tastes.