Regardless of what actual measuement Russell used it's irrelevant. He came up with different measurements at varous times then fudged his own numbers when things didn't turn out as he falsely prophesied.
Rutherfraud sunbsequently condemned the pyramids as "Satan's stone witness" after Russell declared them "God's witness in stone" prior to the 1914 failed prophecies.
And, as punkie eluded to, the Egyptians used a 360 day lunar calendar, Russell used a 365 day solar (Gregorian) calendar. You can't draw a straight line from 607-1914 no matter what system of measurement you use.