python relativedelta get the wrong result

Question

The python function relativedelta calculates the time difference.
However, I get the wrong result.

from dateutil import relativedelta
y=relativedelta.relativedelta(pd.to_datetime('2006-01-11'), pd.to_datetime('1988-09-26')).years
m=relativedelta.relativedelta(pd.to_datetime('2006-01-11'), pd.to_datetime('1988-09-26')).months
y*12+m

207
# should be 208

But the above should be 208 since m should equal to 4 instead of 3.

Another example gets the correct result:

y=relativedelta.relativedelta(pd.to_datetime('2006-01-11'), pd.to_datetime('2003-04-04')).years
m=relativedelta.relativedelta(pd.to_datetime('2006-01-11'), pd.to_datetime('2003-04-04')).months
y*12+m

33
# CORRECT!

y=relativedelta.relativedelta(pd.to_datetime('2006-01-17'), pd.to_datetime('2001-12-20')).years
m=relativedelta.relativedelta(pd.to_datetime('2006-01-17'), pd.to_datetime('2001-12-20')).months
y*12+m

48
# should be 49

Any idea?