Think of shares as equivalent to blocks on the main chain. They have a difficulty adjustment which, like blocks, affects the rate at which they are mined. Ocean has (IMO) their minimum difficulty set a little too high (Braiins uses a more reasonable value). The effect is a lower number of shares within a given unit of time, which also generates a more volatile hash rate graph. Ultimately, though, the number of shares within unit time alone isn’t what defines your contribution – it is a combination of the number of shares + difficulty within unit time that does. A better metric to compare is the average hash rate over time. Obviously if you see a big difference there between Braiins vs Ocean, then that would be a concern. The share count alone just indicates that the two pools are sampling at different rates.