Hello,
At the time of your payment, 100% upvote was worth 3.67 SBD hence that being the upvote you received. I have refunded 2.5 SBD to you so in total you have paid 1.8 SBD for 3.67 SBD upvote.
This should not be a problem in the future as I have now received additional delegation so 100% upvote is worth 8.80 SBD.
Please in the future have a look at my profile and read what it says for 100% upvote worth.