BRRR strategy queries (A 1,00,000 property and running the number

[Blesson Biju Alexander .]

I'm confused about the brrr strategy, about the 70% rule. Let's say, the property is priced up for 1,00,000 & there is an estimated repair cost of 20,000. which totals the money I have to spend to be 1,20,000. 

if the ARV is at 2,00,000. Then if banks refinance for around 70% ( investment property).

They will refinance on 120,000 right? which is 70% of 120,000= 84000. is this right? , because if that's the case, it's a bad deal I suppose as 84000 is a really low amount ? 

Im confused on running numbers on this example