Hello Bayesian peoples :-)

I am running a dichotomous Bayesian Rasch model using the code below on a test consisting of 45 items & 225 respondents. My question is probably stupid but I am not able to understand properly the output of the posterior_epred function. I know I have 10199 columns in the outputs matrix, but what are they? Somebody have more information than those from the help files available in CRAN?

Thank you so much for your answer

```
# Run a Bayesian Rasch model
formula15 <- bf(Xb15 ~ 1 + (1 | It15) + (1 | P15))
prior15 <- prior("normal(0, 3)", class = "sd", group = "It15") + prior("normal(0, 3)", class = "sd", group = "P15")
fit15 <- brm(formula = formula15,
data = X15,
family = brmsfamily("bernoulli","logit"),
prior = prior15)
# Posterior predictive check
ppe15 <- posterior_epred(fit15)
str(ppe15)
```