That's the amount of water, and how its measured with syringes in units and Milliliters/CC's. 1Ml=1cc=100units. Yeah Its better not to use too much water when prepping it IME, especially for plugging anywhere from 50-100 units of water will be fine per 2mg, id use about 30-50 units for anything less, its really not a huge deal its just easier to prep with anything less than 1ml or 100 units of water if your using a spoon as I do. And also, Hopeless soul and crackbaby were right, maybe 3-4" is a bit too far in there id say around 2" is probably more accurate as far as how far to go into the anus, but 1" is a little to close to the outer edge IMO. Sorry its been quite a while since I have plugged anything, but anywhere around 2-3" has always worked for me, its better to have it in there at an angle too so it shoots into the wall and not straight in there, at maybe like a 20-30 degree angle you should be good. And when you look at the side of the syringe though most syringes have numbers with a line next to them. In my case I have 1Ml syringes and they have the numbers 10-100 counting in 10's like 10-20-30-40-50.... on the side with lines next to the numbers. Those numbers/lines are there to measure the solution in units. I have always just used an insulin syringe with the needle pulled out of it to plug, some of them were even the super small 0.3Ml or 30unit size and the 0.5Ml or 50unit size which will also work, especially if your not using more than 2mg of sub. It will absorb it quicker and you have less chance of leakage if you use less water in your solution. A lot of people use oral syringes, which you can buy at pretty much any pharmacy without the hassle that they give to a lot of people trying to buy insulin syringes and they are usually pretty big I believe like 3-5 ml, you can probably get them smaller though, the smaller the better if your plugging. also I was just saying to sit for 10-15 mins to be safe, as I have gotten up to quick before after doing this and lost some of the solution I shot in there, 5 mins would probably be enough honestly, again I haven't done this in a while since I began to IV it sorry I was a little rusty. But I think you got all the right info now, no need to wait on ordering them, just go out to walgreens or cvs(any pharmacy should have them) and look for an oral syringe. remember the smaller the better preferably more than 0.5ml and less than 2ml to be precise, prep up the sub and plug away! Please post if you have any more questions and if not then after you do it and let us know how it goes, I think you'll be satisfied as its much more efficient than sublingual.