I'm not sure I understand. You have instructions that tell you to use a full cup (240 cc) of dilute MG solution on each 5" pot? That's absurd. Put a little in to moisten the soil, and move on. I use a syringe to squirt about 20cc's in on each of my 4" pots every few days. If my pots are under bright lights, they'll dry out faster. If under lights but covered with a big tarp (to keep everyone warm) the humidity stays high, and they stay moist longer. I dilute AP MG about 10:1 for seedlings.

Well, gee, if you're going to throw it on the soil in a garden bed, sure, throw a cup on. Most of it will sink in and disappear. What remains will saturate the soil around the roots. If you pour one cup of liquid on a 5" pot filled with soil, you're just going to make a flood.

Exactly. It is talking about feeding plant transplants in the garden. That is what it is made for. NOT for seedling transplants in a small pots.

Dave

What herbs are you growing? Many don't like rich living and need no fertilising.

Ok, got it. Sorry, I'm kind of new to this. So should I just not fertilize them or get some other kind of fertilizer or what?

You can use that stuff since you have it but you will have to dilute it substantially. I'd go 1/2 strength (1/4 capful) per gallon of water and then as Dan suggested just give each little pot just enough to lightly moisten the soil in it just as if you were watering. 1x per week except for the herbs.

I know the terminology can get confusing when new but normally (whatever that is) when they refer to transplants or plantings they mean plants going in the garden or to the place where they will be grown for the season (if a big container). Until the young plants go to that final growing place they are "seedlings", not plants. Or does that confuse you more?

Dave

This isn't about dumping a certain amount of fertilizer on a plant. It's about adequately wetting the soil with fertilizer so the plant can use it. If the plant is coming up in a thimble, you just need a very tiny bit. If it's coming up in a 5 gallon bucket, you'll need somewhat more.

Think about it this way. With that MG fertilizer, just water the plant with the diluted fertilizer instead of with plain water.

Unless you tell us which herbs you have we can't give you advice. Some don't mind a bit of fertiliser others really don't want it.