Ten? I thought it was only five. May I request the name of whatever source material you found that in?
You are correct, I had to dig pretty deep to find where I made my mistake - it was the discussion of viscid silk used in glue-covered catching spirals which is 10 times stronger than -- well, rather than go into technical details, I will agree that standard spider silk has only 5 times the tensile strength of steel.
I ran across this interesting tidbit:
In their new work, Kaplan and colleagues used genetic engineering to make a cloned spider silk protein that can form films and fibres. By mixing this material with biosilica -- from the proteins of diatoms -- in aqueous solution, the researchers were able to create a new composite nanomaterial with exceptional mechanical properties. The researchers found that the eliptically shaped silica particles attached themselves to the protein fibres, which as a result became "sticky".
Unfortunately, they did not go into too much detail.