Exposure for Ektachrome 64T

[RdL]

I will be doing some experimentation with Ektachrome 64T outdoors, based on a suggestion made by Bruce Barnbaum in a workshop I attended a couple of years ago.  I am a bit confused by the stated exposure recommendations in the Kodak literature and I am wondering if someone can shed some light on them.  A nominally simple question but since I will be shooting 4x5 Readyloads I would like to zero in on the right EI first without burning several sheets just to get an EI.

The film is nominally rated ISO 64 under 3200 K tunsten.  In daylight, one is to use an 85B filter which has an exposure compensation of 2/3 stop, which would take it down to a meter setting of EI 40.  The Kodak publication says to rate the film, in daylight, at ISO 40, which is also 2/3 stop but does not say if this includes the filter compensation.

So the question is do I rate it at EI 40 which includes the filter correction OR do I rate the "daylight = EI 40" plus the filter compensation and set the meter to EI 25 ?

Richard