I did a bit of research on this a few years ago now and from memory I managed to find 4 different definitions of what a "MilDot" is.
Don't worry too much about it though, the definition I use as being true is the distance between the centre of one dot to the centre of the next dot is 1 MilliRadian or 3.44 MOA (It's not the distance between the dots, that's usually 0.8 MilliRadians.
Your Falcon also uses the 3.44 MOA definition of a MilDot so I would consider that to be "True"
Ok you don't really care about any of that though, you just want to know how to use them for your holdovers and possibly for rangefinding.
Chairgun will get you in the right ballpark, but I prefer to trust bits of paper... to that end I knocked up some extremely nerdy practice targets.
These targets need to be placed out at the correct printed range because they are graduated with Mildots at the correct size for that range.
Note: These targets have been updated now - the latest versions can be found at www.anstonftc.co.uk/targets
Print those out, place them out at the correct measured distance and look through your scope to check that the mildots on the targets line up exactly with your scope.. if they don't something's wrong - also check that the 150mm marking on the targets measures 150mm - if it doesn't then you may need to adjust the Print settings in Acrobat to produce a 100% print and not "Print to Fit paper".
Once they all line up, shoot groups at each distance by aiming your crosshairs at the centre of each target (the Red Dot) - you'll then be able to inspect the targets to see exactly what your holdover or holdunder is for each range - for added accuracy, make sure your crosshairs are level when you shoot. i.e. don't "cant" your gun or the results will be slightly wrong.
For example if you put the 40 yard target out and find that your pellets are all landing on the half mildot mark, then that's your holdover for 40 yards - 0.5 mildots. There's no need to measure anything and then convert to mildots, it's all done for you with the exactly sized mildot graduations on each target.
There are also a selection of killzones on each target for you to practice on - the smallest killzone on each target is the smallest killzone allowed in HFT at that distance.