Show Parlay

[theMOUSSEisloose]

I'm new around here so please forgive me if the following questions are dumb. Just making sure this is how Show Parlaying works.

Example:

I bet $100 to show on a horse and it hits for $2.10 so you get $105 back/ Do you pocket the $5 and keept betting $100 and pocketing whatever you get over the $100

or is it like this

I bet $100 to show on a horse and it hits for $2.10 so I get $105 back. I put the $105 on the next one and win say I then have $120 then I put the $120 on the next one?

Sorry if this is a dumb question and thanks for any help.