hi,

just to be safe: you have to send STEEM Dollars not STEEM!
„Just send SBD (at least 0.5 SBD) to @minnowbooster“

your reward reward can be UP TO *3 max

„and receive an upvote worth up to 3 times what you paid.“

it all depends on the current voting power of the bot

„At 100% voting power the bot will give your nominated URL an upvote worth 3 times what you paid in, with the received vote value decreasing proportionately as VP decreases, ie 66% VP yields 2 times, right down to breakeven at 33% VP and a loss if you pay in when the bot has less than 33% VP. (These are gross percentage values, please take into account that on Steem 25% of the post value goes to the curators, in which case the NETT breakeven is actually at 45.67% VP)„

the upvote happens quite instantly within a couple of minutes in my experience, you could just try it with a small amount but as you need the post-url in the memo, i think the post has to be published first