R Package Prediction Function Doesn't Explain Numbers Type

`?predict.xgb.Booster` doesn't show in Value section what the numbers mean if `objective = "survival:cox"`. In contrast, the survival package has a better explanation for its predict function `?predict.coxph`.

> type: The type of predicted value. Choices are the linear predictor (`"lp"`), the risk score exp(lp) (`"risk"`), the expected number of events given the covariates and follow-up time (`"expected"`), and the terms of the linear predictor (`"terms"`). The survival probability for a subject is equal to exp(-expected).