SanDisk 64 GB extreme pro U3 V30

the benchmark results on the card without adapter microsd, say:
Writing speed: 23.2 MByte/s
Reading speed: 22.4 MByte/s
H2testw and other software.
while with the adapter microsd, the benchmark say:
Writing speed: 89.9 MByte/s
Reading speed: 83.1 MByte/s
why in both cases, the speed is not the one declared by sandisk?
thank you