You can download a quick reference guide for EFS formula language at http://groups.yahoo.com/group/eSignal/files/
The file name is efsqrg.doc
Or in eSignal go Help->eSignal 7.0 Info->Formula Reference Guide
I also posted this problem to eSignal and they told me they were aware of this bug.
This problem should be solved with the new release eSignal 7.01 which just came out today.
http://www.esignal.com/download/default.asp