A new Civil Engineer failing to complete his contract worth 70000 pesos in a specified time is compelled to pay the penalty of 1/2 of 1% per day for the first 6 days of the extra time required, and for each additional day thereafter, the stipulated penalty is increased by 10% of 35.00 each day. If he pays a total penalty of 6160 pesos, by how many days did he overrun his contact time?