They have a chart with all the spoke lengths needed based on the spoke end diameter.
This is how they determine it. http://www.extralite.com/Products/measu ... %20SED.htm
" onclick="window.open(this.href);return false;
Seems to me Extralite is calling into question the accuracy of the E.R.D. measurement because what I see described in the link above is synonymous with Sheldon Brown's definition of E.R.D. I am guessing that because they spec high tension for wheel builds with the hubs, Extralite wants hyper accurate ERD but since typically spokes are supplied in 1mm length increments, teh difference is not going to matter unless you have a Hozan spoke cutting tool or similar. I would suggest you use the LB supplied ERD and get the hub tech specs and use the DT Swiss spoke calculator which should give you accurate spoke lengths.