Edit: stepped away so there's been a bunch of posts since I started writing so much of this has already been said, but FWIW:
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Added 2 quarts and barely at "L", I'll add another quart.
So three quarts low.
10W-30 will not hurt your engine or affect the oil level, many forum members run 0W-40, 10W-40, 15W-40 without any issues.
For future reference, IME, the low oil light (assuming it's functioning correctly) begins to come on when the engine is close to one quart low shortly after starting the first (cold engine ) drive for the day, then goes off after a couple of minutes as the engine warms up. As the oil level continues to drop (assuming you're continuing to drive the vehicle without adding oil) the light will come on more frequently, stay on longer, and eventually it will come on and stay on when around two quarts low.
If you check your oil first thing in the morning (cold engine) you may get a false reading IME as some oil has flowed back to the oil pan overnight. This can be exaggerated (false high level) if you're using an old, defective, or just poor design oil filter that empties out overnight as the vehicle sits. Even parking on an incline can change the level of the oil (on the dipstick) somewhat.
IME I drive the vehicle to get the engine at operating temp ie: driving to get fuel, let it sit a minute or three ie: while hooking up the fuel pump handle, then go forward and check the oil level. Pull the dipstick, wipe it off well with a dry/clean paper towel, re-insert the dipstick right side up (so you can read Engine Oil on the handle), count to three (or any number you choose), pull out the dipstick, hold it somewhat tip down so the oil doesn't run up the stick, read the level, anywhere between the hatch marks is OK (if the stick itself has burned-on oil varnish you can clean that off with solvent before hand to help see the level in the future).
If you want to get even more OCD about it, if the stick comes out splattered with oil making it hard to determine the level you can (I have) spray a little Carb/Brake cleaner into the fill tube to clean it out first, then reinsert the dipstick to check the oil level.
Warning: if you do that
hold onto the aerosol can red spray tube and do not stick the plastic tube down into the dipstick tube as it can blow off and go down the hole. IMO a small amount (a few bursts) of a light solvent won't hurt anything, it'll just evaporate in the hot oil.
Question for
@wisemonkey : What oil filter are you using?
If it hasn't been said already, make sure to use a Toyota oil filter (probably the safest) or (IME) a top tier oil filter (Mobil 1 for example). Never WIX or generic white filter from the Quickie Lube shop.