APScheduler run only a limited number of jobs - python-2.7

Question

I realized that APScheduler (3.3.1) with Python (2.7) only run a limited number of my jobs, so I made a test file to check it better, this is my code:
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import datetime
import time
from apscheduler.schedulers.background import BackgroundScheduler
def fetch_job(a):
print a
time.sleep(1)
print a, ' awakened'
scheduler = BackgroundScheduler()
schedules = [
{'source': '1', 'interval': 10, 'job': fetch_job},
{'source': '2', 'interval': 10, 'job': fetch_job},
{'source': '3', 'interval': 10, 'job': fetch_job},
{'source': '4', 'interval': 10, 'job': fetch_job},
{'source': '5', 'interval': 10, 'job': fetch_job},
{'source': '6', 'interval': 10, 'job': fetch_job},
{'source': '7', 'interval': 10, 'job': fetch_job},
{'source': '8', 'interval': 10, 'job': fetch_job},
{'source': '9', 'interval': 10, 'job': fetch_job},
{'source': '10', 'interval': 10, 'priority': 3, 'job': fetch_job},
{'source': '11', 'interval': 10, 'job': fetch_job},
{'source': '12', 'interval': 10, 'job': fetch_job},
{'source': '13', 'interval': 10, 'job': fetch_job},
{'source': '14', 'interval': 10, 'job': fetch_job}
]
for i, k in enumerate(schedules):
scheduler.add_job(k['job'], 'interval', seconds=k['interval'],
args=[k['source'],], next_run_time=datetime.datetime.now())
scheduler.start()
while True:
time.sleep(2)
When i run it Output is like this:
1
2
3
4
5
6
7
8
9
10
1 awakened
No handlers could be found for logger "apscheduler.executors.default"
2 awakened
43 awakened65
awakened
awakened
awakened
7 awakened
8 awakened
9 awakened
10 awakened
In first run, only 10 jobs trigger, while I added 14 job to scheduler, but when scheduler trigger for second round and so on, I see other jobs too.