There's no specific adjstment to "adjust the transfer slot".
What changes it, is the idle speed adjustment screw... the one that the throtle linkage comes to rest against at idle.
The goal is to back the idle speed adjustment screw off until the blades are in the correct relationship to the transfer slot, by opening the secondary blades, using their screw, to let in enough air.
Easiest way to do it, is to adjust the idle speed correctly on the car, the normal way; take the carb off and turn it upside dow; observe the transfer slot, and how far the primary blades are away from the desired relationship; and adjust the idle speed screw while watching for the correct relationship. Then adjust the secondary adjustment to change them an equal and opposite amount to what you changed the primary ones. For example, if you closed the primary throttles .050" to get the slot right, open the sec blades .050". Put the carb back on and see where you are. Repeat until perfect. On some carbs, you can take the sec screw out and turn it upside down, so that its head is accessible from above. Not sure about the Street Adventure carbs.
LEAVE THE SQUIRTERS ALONE!!!!! They are the VERY LAST thing to adjust anything about, until every other detail about the carb has been dialed in. From the point of view of carb design, they are merely a Band-aid for the carb's inability to deliver fuel as quickly in a throttle transition as it delivers air. The better you get the carb tuned, the less they are needed. They are almost always TOO BIG, and feed TOO MUCH GAS, and are one of the reasons Holleys have a bad reputation for poor gas mileage. People use them too much.
The correct way to tune a Holley for the street is to first get the ignition timing right. Usually this means limiting the mech advance in the dist so that when the "total" (static plus mech, no vac) advance is at the 36° or so that it needs to be for best power and efficiency without detonation, the static can be at around 16-18°. Meaning, NO MORE THAN 20° of mech advance. Most stock distributors give 26-28°, which results in the static (low-speed) timing being WAY too retarded. Inadequate advance at low speeds will make the motor generally run lazy, no "snap" to the throttle.
Once you get that set right, move to the carb. Get the floats right (pri with the level just barely below the sight plug, sec the fuel level should be about .050" below the sight plug), and do the transfer slot setting as described above.
Next thing to do to the carb is to set the main jets right. Holley main jets are usually a couple of sizes too large. Get yourself a few sets of jets, maybe 2 sizes larger than the stock ones, and 2, 4, and 6 sizes smaller. (a change of 1 size is imperceptible; 2 sizes is a fine tweek; 3 sizes is a standard step; 4 sizes is a large step; 5 sizes is HUGE) Decrease the jet size and drive the car on a normal road in a normal way. Keep dropping the size until it just begins to surge going up a slight hill inthe higest gear at the lowest speed you would customarily drive at; then go back up 2 sizes from there. Ignore all other behavior, good or bad, while making this test.
Then get yourself some power valves. Holley almost always puts too low of a number in their street carbs, meaning, no power enrichment occurs until you have given the car ALOT of throttle, which is why they make the jets too big. Raise the PV in steps until the bog goes away.
THen last, tune the secondaries. Find the loosest spring that prevents a bog when flooring it from a stop, and then out the next stiffer one in. You'll probably end up with the brown one; almost cetainly not the yellow one. Then set the sec jets for max mph in the ¼.
If you tune up a Holley by this method, you'll be able to get better driveability and gas mileage than you ever thought possible. As well as spark plug life.