Всё правильно считает питон.
l = {'14':1933,'24':1934,'25':1964,'26':1985,'34':1955,'35':1978,'36':1955,'44':1932,'45':1944,'46':1980,'47':2000,'54':1984,'64':1955}
print(f"l.get('25') - l.get('24') = {l.get('25')}-{l.get('24')}={l.get('25') - l.get('24')}")
print(f"l.get('25') - l.get('44') = {l.get('25')}-{l.get('44')}={l.get('25') - l.get('44')}")
print(f"l.get('26') - l.get('25') = {l.get('26')}-{l.get('25')}={l.get('26') - l.get('25')}")
print(f"l.get('26') - l.get('64') = {l.get('26')}-{l.get('64')}={l.get('26') - l.get('64')}")
print(f"l.get('34') - l.get('24') = {l.get('34')}-{l.get('24')}={l.get('34') - l.get('24')}")
print(f"l.get('34') - l.get('44') = {l.get('34')}-{l.get('44')}={l.get('34') - l.get('44')}")
print(f"l.get('35') - l.get('34') = {l.get('35')}-{l.get('34')}={l.get('35') - l.get('34')}")
print(f"l.get('35') - l.get('36') = {l.get('35')}-{l.get('36')}={l.get('35') - l.get('36')}")
print(f"l.get('36') - l.get('14') = {l.get('36')}-{l.get('14')}={l.get('36') - l.get('14')}")
print(f"l.get('46') - l.get('34') = {l.get('46')}-{l.get('34')}={l.get('46') - l.get('34')}")
print(f"l.get('46') - l.get('36') = {l.get('46')}-{l.get('36')}={l.get('46') - l.get('36')}")
print(f"l.get('54') - l.get('25') = {l.get('54')}-{l.get('25')}={l.get('54') - l.get('25')}")
print(f"l.get('54') - l.get('64') = {l.get('54')}-{l.get('64')}={l.get('54') - l.get('64')}")
l.get('25') - l.get('24') = 1964-1934=30
l.get('25') - l.get('44') = 1964-1932=32
l.get('26') - l.get('25') = 1985-1964=21
l.get('26') - l.get('64') = 1985-1955=30
l.get('34') - l.get('24') = 1955-1934=21
l.get('34') - l.get('44') = 1955-1932=23
l.get('35') - l.get('34') = 1978-1955=23
l.get('35') - l.get('36') = 1978-1955=23
l.get('36') - l.get('14') = 1955-1933=22
l.get('46') - l.get('34') = 1980-1955=25
l.get('46') - l.get('36') = 1980-1955=25
l.get('54') - l.get('25') = 1984-1964=20
l.get('54') - l.get('64') = 1984-1955=29