a few people have already said this, but sometimes it's helpful to get advice explained differently.
check how many people advance from the first round to second. i'll use 20 as an example. check the psych sheet for who's competing in what event. if 20 people advance, then you can assume that the top 20 will make the second round. if you are faster than the slowest person in the top number of people advancing, that would be how fast you need to be. just bare in mind that even if you could make it to the second round based on the psych sheet, that doesn't mean that you will.