You can find the manual for the Flytec 6030 here:
http://download.naviter.com/flytec/6030/Manuals/Flytec6030_EN_V321.pdf.

Flytec USA has a different Flytec 6030 manual but it is only available to pilots
who purchase their 6030 from Flytec USA and then only in paper format.

Here's graphic from the 6030 manual linked to above:

Note the Speed to Fly indicator on the right hand side of the display. This
graphic indicates that the proper speed to fly given the conditions displayed
should be 42 or 43 km/h. (You'll observe that there are a few problems with the
values shown.)

The manual states: The thick arrow visible on the hand right side of the
analogue speed scale informs the pilot about the speed for best glide, dependent
on the polar, the wind and rising or respectively sinking of the surrounding
air. In competition, a pilot will always fly faster than this speed indicator is
recommending, except when every meter of height is essential.

This would normally be referred to as best glide speed not as speed to fly. The 
second sentence indicates that the manual author is aware of the fact that speed
to fly as we know it takes into account one's expected climb rate of the next
thermal.

Let's find the definition of speed to fly:

https://en.wikipedia.org/wiki/Speed_to_fly

Speed to fly is a principle used by soaring pilots when flying
between sources of lift, usually thermals, ridge lift and wave. The aim is to
maximize the average cross-country speed by optimizing the airspeed in both
rising and sinking air. The optimal airspeed is independent of the wind speed,
because the fastest average speed achievable through the air mass corresponds to
the fastest achievable average groundspeed.

So I think that we can conclude that this graphic is a mess (which
is one of the many reasons why Flytec USA has its own manual) and that the right
hand arrow is not the Speed To Fly Arrow, but the Best Glide Speed Arrow.

Anyone reading this manual will quickly see that it is a mess.

I, thankfully, have never used this arrow to tell me the speed to fly (can't see
it anyway), but rather, like I assume almost all hang glider pilots who fly with
the Flytec 6030, I use the MacCready indicator to determine at what speed I
should fly.

You can find an in depth discussion of that technique here:

http://www.andrewvanis.com/HangGliding/McCready_display_and_sounds_users_guide_Flytec_5030/

Unfortunately the Naviter Blade does not have a MacCready indicator nor a
MacCready ring nor does it calculate and display the average climb rate (over a
specified time interval) in the last thermal, unlike the 6030.

The documentation for the Blade (Oudie) states that it has a speed to fly
indicator (they mean a variable value that is displayed if you choose to do so)
that takes your preset MacCready value (in my case a climb rate of 200 fpm) and
sink rate into account.

I have reported that the STF values reported by the Blade are way too low. The
funny part is that the values are fine when you run  a simulation using
your IGC file, but those are not the values displayed when you actually fly the
flight.

At the moment Naviter has stated that their top priority is to get the STF
values to be correct. Personally I think I have a pretty good idea of how fast I
should be flying at any given time, but I have often been wrong. It would be
nice to have a second opinion.