select
  concat(10*floor(age/10), '-', 10*floor(age/10) + 10) as `range`,
  count(*) as count
from (
  select
    TIMESTAMPDIFF(YEAR, customers.birthdate, CURRENT_DATE()) AS age
  from
    customers inner join vehicles on customers.id = vehicles.customer_id
   where
    customers.birthdate IS NOT NULL
    AND vehicles.branch_code = 'H360'
) as t
group by `range`
ORDER BY `range`