My campaign indicates 138 Filled out Form on landing page. However, data collected Campaign members only showed 117. why is that so?

Hi - did you run tests on the landing page prior to sending it public and have test people fill out the form? It'll register every form fillout, including internal tests.

Underneath the landing page stats does it say "All Time"? You can click on the Report Settings link just there and change the dates that the stats are picking up on, so you can specify the day you launched which might help you weed out some of the test data (depending on how many tests you did on the day you "launched" the page...)

Hi - haven't tested it myself yet/or payed attention to it, but could it be that if a lead completes a form multiple times this is each time registered as a seperate form fill out, despite the fact that the lead is already counted as a campaign member.

One way to troubleshoot: create a smart list for anyone who filled out the form.  Something like this:

If the number is over 117, you might check those who fill out the form multiple times (per Jonas)

You can also compare those who filled out the form but are not in your smart campaign: