Incorrect histogram display

I have tried to plot two sets of data in a histogram!
the data sets looks like this:

>>> df = load_diffae()
>>> print(df.shape)
(360000, 5)
>>> dfn = load_diffne()
>>> print(dfn.shape)
(360000, 5)

Both have 360000 rows

However, if you look at the histogram, it looks like the new data set has significantly more rows (shown on the Y axis) than the old data set. What could be the reason for this?

my code:

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import norm
from Extract_elevation import *

def load_diffae():
    df = dfl
    return df 

def load_diffd():
    dfn = dfld
    return dfn 

def Plot_show_eu(df,dfd, dfn):

    x = dfe['O18ad']
    z = dfne['O18nd']
    bins = np.linspace(-50, 1, 40)
    bins = 'auto'
    plt.hist(x, bins, alpha=0.65, label='alt')
    plt.hist(z, bins, alpha=0.65, label='new')
    plt.legend(loc='upper right') 

>Solution :

The bins are chosen differently, so more values enter each bin for larger bins and the plot appears "bigger".