Were they advertised as 100ml? I quickly checked various bottles and GCs and syringes and thankfully the iBottles' 30ml unicorn is a generous 30ml (approx. 34ml to the brim). Phew, that's a relief!
I did buy one 5ml blunt point syringe from Creme de Vape to see if it was any different to my medical syringes and it was different. My medical syringes are accurate (when the markings are still showing) and very slightly pessimistic which is the way it should go whereas the Creme de Vape syringe was less than 5ml to the 5ml mark. Luckily it looks very different so no need to bin it, I just won't rely on it for accuracy, just use it to decant or fill tanks.
Cheers for that, I probably wouldn't have gotten round to checking if not for your post (and while I was at it, cleaned out a load of syringes and bottles and tips!). Ah the things we do for vaping