Congrats on your win, your ticket should pay out 25 units in total as it should include your original stake, if the return is below that amount you should contact support and ask for a correction.
Sportsbooks rarely have that type of mistake but I guess it still happens once in a while. I remember being in a similar situation but in my case, they overpaid my ticket and they told me to keep it since I was a regular on their sportsbook.
I have experienced this once previously at a different sports books. I haven't mentioned the name of this site up to this point as I don't believe it was nefarious. However I was only paid 12.5 units. Currently my case is in dispute.
Thank you very much for taking the time to respond on this one. Much appreciated.