Closer to a TBS in a gallon and a TSP in a liter.
Maybe the difference is in the seaweed products we are using but if I added 1 TBSP of my current extract to 1 gal of water, it would very much discolor the water. Like a stout beer.
I use grandma's method of measuring, too... but only after I've gotten more specific instructions from someone about something new, tried it myself and verified that I'm not WAY off base with my estimations. After that, I just eyeball amounts.