Tires: secondary tire rating number, bmw x5, load index

Question
I recently went looking for tires for my BMW X5, the OEM recommends 235/65-17 104H, I currently have the Nokian Hakka... M/S 235/65-17 108H but my local dealer has 235/65-17 103H, but won't sell/mount them without any explanation.

Since the tires are all the same size, what does the 104 or 108 or 103 number mean?

Answer
Stacy,

Those numbers are caled the Load Index.  They indicate the load carrying capacity of the tire.  It is important that tires have enough load carrying capacity otherwise the tire could fail from overloading.

However, a 103 and a 104 are very close and, in my opinion, close enough.  I am surprised that he wouldn't go ahead as the risk is pretty low.