reaching a child via LimitToLast()

I have the path up until "History" then I'm trying to reach the last child under it to get its "HRV" data.

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I've used OrderByKey().LimitByLast(1); but I don't know how to access the "HRV" of the last child.

Code so far:

DatabaseReference LastHistoryEnrty = DBreference.Child("users").Child(User.UserId).Child("History");

var query = LastHistoryEnrty.OrderByKey().LimitToLast(1);

var LatestHRV = query.Result.Child("HRV").GetValueAsync();

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