I'm using the formula from the official Steem JS Library. After some debugging I've found the cause for this:

Your exact reputation is '1000995952600'. The 4 leading digits that are being used for further calculation are in your case '1000'. The result for Math.log(leadingDigits) / Math.log(10) is < 3.0, but it should be >= 3.0 in this case.

I will report the bug on GitHub after I've fixed it on SteemWorld ;)
Thanks for your report!