
One of the most important things to remember when using your HUD stats is to be aware of the sample size. I have seen people make this mistake time and time again and I have done it many times myself. Some stats require as little as 20 hands or so to be relatively reliable. Some need 100. Some need 500. Some need 1000. I will list some rough rules of thumb here on what kind of sample sizes I think you should be looking for with certain stats.

As you can see some stats like VPIP and PFR come close to their true value over a relatively small sample size. However you should still have about 20 hands before you start making any judgements based off of them. Some other stats require a couple hundred hands. And the river and 4bet stats (which you will rarely use anyways) require such an enormous sample that I think it’s a waste of space to even have them on your screen.
The reason why the sample size requirements vary so widely is pretty simple. With some stats such as VPIP, you (or someone else) has a chance to perform that action almost every hand. Whereas with a stat like river CB, how many times do you even go to the river in say a 100 hands? Not very many.
If you are ever in doubt regarding the relevance of a particular stat, it is a good idea to bring up the full popup and see if there is a number in brackets to the right of it. Here is an example.

In the above popup you can see that the number in brackets to the right of this player’s VPIP is 83. This means that he has had 83 opportunities to VPIP. With a sample this big we can be very confident that the information here will be reliable.
However, if you look at the number to the right of this player’s river fold to CB, you can see that he has only had one opportunity. So the information that we have for that stat is going to be pretty much meaningless. In between those two extremes we can see that this player has had 8 chances to raise a CB. We can be reasonably confident that this player does not raise cbets very often.
The suggestions that I outlined above are just rough guidelines. I am definitely not any kind of stats expert. The main point here is that you need to constantly be aware of the sample size when using your HUD stats to make poker decisions. Bad information can be worse than no information at all. You don’t want your HUD working against you!