what are the parameters of bayes optimization for tuning parameter?

I am using Bayesian optimization to tune the parameters of SVM for regression problem. In the following code, what should be the value of init_grid_dt = initial_grid ? I got the upper and lower bounds of the sigma and C parameters of SVM, but dont know what should be the initial-grid?

In one of the example on the web, they took a random search results as input to the initial grid.

ba_search <- BayesianOptimization(svm_fit_bayes,
                                   bounds = bounds,
                                   init_grid_dt = initial_grid, 
                                   init_points = 0, 
                                   n_iter = 30,
                                   acq = "ucb", 
                                   kappa = 1, 
                                   eps = 0.0,
                                   verbose = TRUE)