The portfolios have 2,3 and 4 coins, this is just a static rule. The concept is the lower the portfolios risk tolerance, the higher the coins' market cap. This means a conservative portfolio would have the top 2 coins (see https://coinmarketcap.com), the moderate would have the next 3 and aggressive has the next 4.

The market caps are normalized (the algorithm is secret for now) to make sure we don't expose anyone to too much risk if a coin does something like pumping into a high position right as we change our portfolio makeup.

As a rule, the higher an assets market cap, the less room it has to grow but also less likely to drop, hence by selecting the top 9 coins we're providing a diversified portfolio that matches the risk tolerance implied by the name.

Fun Fact: If those portfolios don't have what you want, custom portfolios went live a few minutes ago.