I would like to display some information on the first page home, but I don't know and I can't find any formulas.
Which is the formula to display:
no. active categories use on site
no. active regions use on site
no. active cities use on site

for no active ads I have: <?php echo osc_total_active_items() ?>
for no users registered I have: <?php echo osc_total_users() ?>

something similar to what is in the picture attach.

I can't find these formulas on the internet, can you help me?

@danads
Summary functions does not exists for every combination/element. Some of them are created for it's purpose in theme or plugin.