[JackDinn]

yea , its a long story , spent over a year trying to get the upload to work properly for 100% of people & systems.

Its the faster upload connections that sometimes have a spike at the very beginning of the internal measurement method which gets averaged into the rest of the test. I shan't go into it all here.

you can either increase the clipping time to cut of the first few secs of the upload throughput.

EDIT:-
o and if you have been using multi-threads in the upload configs then switch them back to 1 thread.
END EDIT.

OR switch to using the adapter hook measurement method. (configurations / general tab / bottom right tick box "Use adapter hooks.....") (dont forget to choose your correct network adapter in the dropdown list right next to it).

Using your adapters data is extremely accurate but does have a drawback of measuring any other throughput at the time of testing so if you have a lot of LAN traffic using the same adapter this can be a problem.
EDIT:-
Although you can set the configs to check for any throughput before running a test and if it finds there is data flowing already it will quit that particular test.