How do I config character space size for the dashboard header?

I found a screenshot in share your alpha theme:
So I use the same ASCII art in my alpha config:
local status_ok, alpha = pcall(require, "alpha")
if not status_ok then
    return
end

local function footer()
  local plugins_count = vim.fn.len(vim.fn.globpath("~/AppData/Local/nvim-data/site/pack/packer/start", "*", 0, 1))
  local datetime = os.date("  %m-%d-%Y   %H:%M:%S")
  local version = vim.version()
  local nvim_version_info = "   v" .. version.major .. "." .. version.minor .. "." .. version.patch
  return datetime .. "   Plugins " .. plugins_count .. nvim_version_info
end

local dashboard = require("alpha.themes.dashboard")
dashboard.section.header.val = {
  "⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣠⣤⣤⣶⣶⣶⣶⣶⣦⣤⣤⣀⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⣤⣶⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣦⣄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣠⣾⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣠⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣦⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⢀⣾⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣄⠀⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⢀⣾⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣆⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⣼⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡄⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⢰⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣧⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⢸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠸⣿⣿⣿⣿⠿⠿⠿⢿⣿⣿⣿⠿⠿⠿⣿⣿⣿⣿⣿⣿⣿⡿⠿⠿⢿⣿⣿⣿⡿⠿⠿⢿⣿⣿⣿⡿⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⢿⣿⣿⣿⡄⠀⠀⠸⢿⣿⠟⠀⠀⢠⣿⣿⣿⣿⣿⣿⣿⣧⠀⠀⠘⢿⣿⡿⠁⠀⠀⣾⣿⣿⣿⠇⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠘⣿⣿⣿⣿⣦⡀⠀⠀⠀⠀⢀⣴⣿⣿⣿⣿⣿⣿⣿⣿⣿⣷⣄⠀⠀⠀⠀⢀⣠⣾⣿⣿⣿⡟⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⣿⣿⣿⣿⣿⣿⣿⣷⣾⣿⣿⣿⣿⣿⣿⠟⢹⠛⢿⣿⣿⣿⣿⣿⣿⣶⣿⣿⣿⣿⣿⣿⣿⡆⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠀⣸⡀⠀⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡇⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⠹⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣠⣼⣿⣷⣤⣸⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠁⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡿⠋⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠉⠉⠉⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⡏⠉⠉⠉⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢻⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀",
    "⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠉⠈⠉⠁⠈⠉⠁⠉⠉⠀⠉⠉⠈⠉⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀",
}

dashboard.section.buttons.val = {
    dashboard.button("f", "  Find file", ":Telescope find_files <CR>"),
    dashboard.button("e", "  New file", ":ene <BAR> startinsert <CR>"),
    dashboard.button("p", "  Find project", ":Telescope projects <CR>"),
    dashboard.button("r", "  Recently used files", ":Telescope oldfiles <CR>"),
    dashboard.button("t", "  Find text", ":Telescope live_grep <CR>"),
    dashboard.button("c", "  Configuration", ":e ~/.config/nvim/init.lua <CR>"),
    dashboard.button("q", "  Quit Neovim", ":qa<CR>"),
}

dashboard.section.header.opts.hl = "Include"
dashboard.section.buttons.opts.hl = "Keyword"
dashboard.section.footer.val = footer()

dashboard.config.opts.noautocmd = true
alpha.setup(dashboard.config)
However, what I get is:
I looked at alpha.nvim docs, but could not find a solution.
goolord / alpha-nvim

How do I config character space size for the dashboard header? #146
