r – Unexpected horizontal line by ggplot2

I drawed a plot with points and a horizontal line. Below is the example code:

dt <- data.frame(ID = c("Line",
                        "P1",
                        "P2",
                        "P3"),
                 Year = "2016",
                 Value = c(1, 0.533, 1.233, 0.233))

dt$Value <- format(dt$Value, digits = 2)

# Unexpected horizontal line
ggplot(NULL) +
  geom_point(data = subset(dt, ID != "Line"),
             aes(x = Year, y = Value, color = ID, shape = ID)) + 
  geom_text(data = subset(dt, ID != "Line"),
            aes(label = subset(dt, ID != "Line")$Value,
                x = Year, y = Value)) +
  geom_hline(yintercept = as.numeric(subset(dt, ID == "Line")$Value),
             color = "red") +
  theme_bw()

However, the Figure below seems strange: the red horizontal line is on the y-axis of 0.23, not 1. Why does this happen? Thanks!