I use a small screwdriver , the difficulty for me is to move the lever as little as possible.
Mostly you overshoot and have to correct the next time in the other direction.
For me its a matter of trial and error to arrive to the desired accuracy at last.
Let us have your experience.
PS :I am not very handy with such delicate small things.
Gen 1963 Omega Seamaster Deville , received new at that time as present from my fiancee (now wife).
This watch is still in perfect working order and keeping time accurately.
The lever for coarse time adjusting is marked "rate" in the picture below.
As said and in order to access it you need to remove the rotor and the plate holding the auto winding gears.
This is only required if the fine tuning (with the screw) is not enough.
And yes , dont touch the other lever (marked "beat") unless you have propper beat measurng equipment.
To let it run faster you turn the screw to the +
To let it run slower you turn the screw to the -
One division on the scale is about 5s/day.
So in your case , turn the scew 2 to 3 divisions towards the - and check timing again.
This is a fine regulation and the screw head is excentric so that you need not to turn it outside the graduated scale.
If the deviation is outside the reach of this screw (+15/-15 s/day) the regulator lever is to be moved like you do on your a7750. Here this lever however is located underneath the windig unit so that you have to remove it before you can alter its position.
If this is a daily average under your wearing + resting conditions , leave it that way , its excellent.
You can try to improve it without regulating by trying several resting positions (eg crown up , dial up , etc) and see if you can compensate the deviation during the wearing time.