Very possibly I don't understand what we're looking at, but it looks to me like you have an unusual crank arm fixing bolt that does away with the need for a dustcap. Like [MENTION=452633]52telecaster[/MENTION] said, an 8 mm should take the bolt off; and then I expect you'll be able to fit the standard crank puller.
Judging by this photo that I found on Google, there is slightly oversized recess, into which the flange of the fixing bolt fits, andthe puller threads start just below that.
The problem with this theory is that according to the website, the "Cranks are sold without bolts or dustcaps." Where did you get the fixing bolts?
(edit

Oh, wait... maybe this explains it:
https://www.planetx.co.uk/i/q/CSHOLS...rankset-spares