Although that is cheating...
If you want to come to around 90% by 'calculating', then you need to do some maths first. You must calculate the stuff backwards, thus starting from 90 (which is the variable 'amount').
First of all you need to understand what the script exactly does before you can edit it.
As such, the script calculates a score (variable 'LoveCount') based on the amount of occurances of the letters L,O,V,E,Y,O and U in both your names. The higher this score, the more you two are in love, so the legend goes.
At the end of the calculation, the script also takes the length of both your names into account to get to the final score (variable 'amount'). The bigger the difference in length, either the lower the score will drop again, or the higher score you will raise. This because it is also important what name you enter first.
So, the easiest thing is to change the letters it checks for. The more letters you have in common in your name with these letters, the higher the score.
The harder thing is to change the actual calculation so it favors your names.