The paellas in the cookbook have the proportion of ingredients for 8 individuals based on the assumption that  .2875 cups of raw rice, when cooked with the other ingredients, is the proper quantity for each individual. The rice then for 8 totals 2.3 cups of rice .  

 In the likely event you will want to modify both the proportion of rice for different groups of friends and the number of friends invited. The following system will allow you to do so.

 First a word about proportions.

.29 cups of raw rice per person if it is an adult mixed crowd

.35 per person if the crowd is younger

.4 per person when the party is mostly hungry young men.

 This also assumes that there will be tapas served while the paella is made or appetizers of any kind.

First you determine how hungry your crowd is.:

Select a quantity of dry rice per person, determine how many of you there will be and then determine how many cups of dry rice you will need. Example: if you have 6 guests who are extremely hungry assume .5 cups of dry rice per person. Then 6X.5=3 cups. You will need a pan that accomodates 3 cups of rice

Then you pick the Paella pan: 

All pans are measured from top rim to top rim and do not include handles. By multiplying the number of guests by the rice per person determination you make, you will get the total quantity of rice you will require. )Select the line in the table with the total quantity of rice that most approximates your calculated total quantity. On the same line you will find the dimension of the pan that you should use. (from above example we are looking for a pan that has 3 cups of rice as optimal quantity for pans dimensions. The answer is a 50 cm pan ) If you are stuck between pans, you can increase  (not decrease) the quantity of rice by up to 20%. If this is inadequate for your need you should select the next higher paella pan, use the optimum quantity of rice and count on leftovers.

A further note on paella is that in order for the rice to be uniformly and properly cooked Paellas are always shallow and the finished paella never exceeds the level of the handle ratchets.  

                                                                        Yes

                                                                          No!

Now that you have selected the proper paella pan you now need to select a multiplier for your ingredients :

The multiplier is based on the rice total of 2.3 cups and the calculation is the total rice your party requires divided by 2.3 cups. The table has these multipliers for the optimum cups of rice for each pan. If you have a rice total in between these optimum levels, you will have to make the calculation yourself. The multiplier applies to every ingredient in the paella. In the above example you would scale all ingredients by 1.3.