You mean white stuffing under the white end-cap?
And do you know the capacity of the carto? Boges (about 1 3/8 inch long) are around 1ml. But Echo may have 3ml - I have no idea. You need to know the capacity of your carto.
I recommend thinner juices, 70pg/30vg or thinner and I find thin clear juices with no sediment make a carto work well longer.
I do this
shake and uncap the
eliquid
hold a bit of tissue on the threaded end.
Tilt the carto and drip 18+ drops per ml capacity into the carto, slowly and rotating to drip on drier areas
Clean up the threaded end so it's dry and clean.
Then tilt the open end down into tissue and blow into the threaded end to clear the central air channel (if it has one).
I fold a bit of tissue and clean up any loose liquid above the stuffing
Recap the carto or put a plastic or delrin drip tip on it as a mouthpiece
Then comes the settling to make sure every bit of stuffing is damp so I don't singe the carto. I lay the carto on different sides for 15-20 minutes. If your juices are thicker than mine then you may need to let cartos soak/settle a lot longer. (like some people do overnight)