Code runs without error but results don't make sense

[Cal]

Here's the code:

from __future__ import (absolute_import, division, print_function, unicode_literals)

import datetime
import backtrader as bt
import backtrader.feeds as btfeeds
import yfinance as yf

import backtrader.analyzers as btanalyzers
import backtrader.strategies as btstrats

# Create a strategy
class SmaCross(bt.Strategy):
    # list of parameters which are configurable for the strategy
    params = dict(
        pfast=9,  # period for the fast moving average
        pslow=80   # period for the slow moving average
    )

    def __init__(self):
        sma1 = bt.ind.SMA(period=self.p.pfast)  # fast moving average
        sma2 = bt.ind.SMA(period=self.p.pslow)  # slow moving average
        self.crossover = bt.ind.CrossOver(sma1, sma2)  # crossover signal

    def next(self):
        if not self.position:  # not in the market
            if self.crossover > 0:  # if fast crosses slow to the upside
                self.buy()  # enter long

        elif self.crossover < 0:  # in the market & cross to the downside
            self.close()  # close long position

cerebro = bt.Cerebro()

data = bt.feeds.PandasData(dataname=yf.download('AAPL', '2013-01-01', '2017-12-31', auto_adjust=True))

cerebro.adddata(data)

cerebro.addstrategy(SmaCross)

cerebro.addanalyzer(btanalyzers.TradeAnalyzer, _name='myanalysis')
thestrats = cerebro.run()
thestrat = thestrats[0]
result = thestrat.analyzers.myanalysis.get_analysis()

# Printig Analyses:
print("Total Trades: ", result.total.total)
print("Gross Total: ", round(result.pnl.gross.total,4))
print("Average/Trade: ", round(result.pnl.gross.average,4))
print("Bars per Trade: ", round(result.len.average,2))

# cerebro.plot()

This results in:

[*********************100%***********************]  1 of 1 completed
Total Trades:  12
Gross Total:  11.8395
Average/Trade:  1.0763
Bars per Trade:  67.73

Process finished with exit code 0

It's a trade and reverse system (always in). Why wouldn't BarsPerTrade*TotalTrades = TotalTradingDaysInPeriod - slowSMA?

[Cal]

I duplicated the strategy in Excel. Everything looks good except Bars per Trade. Should be 147.5 instead of 67.73.