Conditional Logit中predict函数手动计算不匹配问题求助

我正在理解Conditional Logit模型中predict函数的工作原理，尝试手动计算预测值，但结果和函数输出不一致，恳请提供帮助。

相关代码如下：

library(survival)

set.seed(1)
data <- data.frame(Used = rep(c(1,0,0,0),1250),
                   Open = round(runif(5000,0,50),0),
                   Strata = rep(1:1250,each=4))

mod <- clogit(Used ~ Open + strata(Strata),data=data)

newdata <- data.frame(Open = seq(0,10,1),Strata=1)

risk <- predict(mod,newdata=newdata,type = "risk")
risk


lp <- predict(mod,newdata=newdata,type = "lp")
lp


## 手动计算部分
coef<-data.frame(coef = summary(mod)$coefficients[,1],
                 se= summary(mod)$coefficients[,3])
coef$se <-summary(mod)$coefficients[,3]
coef$UpCI <- coef[,1] + (coef[,2]*2) ### 这里用2简化计算，实际可使用1.96
coef$LowCI <-coef[,1] - (coef[,2]*2) ### 这里用2简化计算，实际可使用1.96

fitted<-data.frame(Open= seq(0,10,1))

fitted$Marginal <- exp(coef[1,1]*fitted$Open) /
  (1+exp(coef[1,1]*fitted$Open ))

fitted$UpCI <- exp(coef[1,3]*fitted$Open )/
  (1+exp(coef[1,3]*fitted$Open))

fitted$LowCI <- exp(coef[1,4]*fitted$Open )/
  (1+exp(coef[1,4]*fitted$Open ))

内容的提问来源于stack exchange，提问作者Pam G