Confused about a form

[PGspy18 1]

I'm reading through the manual, and i get to page 3-7. I figure i should practice using the form, so i go to 3-5 to find what number i get if i am landing at KSFO (altitude 13 ASL) but i realize none of the numbers are below 630, when it says on 3-7 that the final number can not exceed 630. i dont get it, is there some trick to fill out the form correctly?

[pschlute 37]

I am no an expert but i think the form/charts works as follows....if you are landing at higher temperature/altitude/shorter runways your maximum landing eight will be reduced. As you work down the form things like autobrake inop/anti ice/tailwind will reduce it further. You can end up with a max allowable weight limit BELOW the aircraft's structural landing weight limit.

 

 

However a landing at a long/normal runway with few limiting factors will leave you with a figure higher than the "structural landing weight " limit of 630k lbs. In that case you are only limited by the 630k lbs figure.

 

Peter