Maybe you remember this from doing this at school.
We take both names and count the amount of the letters L, O, V, E and S for each name and then sum them up until we have a number of 100 or less.

Example

Lets take 'Lisa LOVES Jake' for example:

There is 1 L, 0 O's, 0 V's, 1 E and 1 S. So, this will make the number 10011.
Now we're going to sum them like this: 1+0, 0+0, 0+1, 1+1. Which is 1012. Then, we'll do the same all over again and eventually, we'll end up with their Odds Of Love: 24%.

Poor Lisa and Jake. But, luckily, it's just a fun game! So, never take it serious.
If you like someone, just go for it!