Usually you’ll see the pistils/stigmas show more obviously before full grown calyxes are apparent (in my experience)
It’s hard to tell from the pic tho - I bet you’ll see some action within 7 days
If you want to speed up the sex of the plant start reducing the hours of light by an hour every other day till you get to 14-10 then give it a day or two you’ll see her open up and show you then you can go back to the 18/6 if you like or drop to the 12/12 . Hope this helps