Bad iperf result on 2.4GHZ between pc and MR200

Hi all

on the tp-link mr200 :
iperf3 -s

on my pc connected on 2.4ghz ( no support for 5ghz on LEDE MR200 ) :

Connecting to host 192.168.1.1, port 5201
[ 4] local 192.168.1.233 port 57242 connected to 192.168.1.1 port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 2.88 MBytes 24.1 Mbits/sec
[ 4] 1.00-2.00 sec 2.62 MBytes 22.0 Mbits/sec
[ 4] 2.00-3.00 sec 3.00 MBytes 25.2 Mbits/sec
[ 4] 3.00-4.00 sec 2.38 MBytes 19.9 Mbits/sec
[ 4] 4.00-5.00 sec 2.38 MBytes 19.9 Mbits/sec
[ 4] 5.00-6.00 sec 2.38 MBytes 19.9 Mbits/sec
[ 4] 6.00-7.00 sec 3.12 MBytes 26.2 Mbits/sec
[ 4] 7.00-8.00 sec 2.88 MBytes 24.1 Mbits/sec
[ 4] 8.00-9.00 sec 2.88 MBytes 24.1 Mbits/sec
[ 4] 9.00-10.00 sec 2.62 MBytes 22.0 Mbits/sec


[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 27.1 MBytes 22.8 Mbits/sec sender
[ 4] 0.00-10.00 sec 27.0 MBytes 22.6 Mbits/sec receiver

My wlan0
Encryption: WPA2 PSK (CCMP)
Channel: 8 (2.447 GHz) | Tx-Power: 20 dBm
Signal: -72 dBm | Noise: 0 dBm
Bitrate: 60.6 Mbit/s | Country: FR

Operating frequency N
Channel 8
Width 40 Mhz

is it normal ?