Hcg quadrupled in 48 hours??

Due to a chemical in July, my doctor sent me for beta hcg after a faint line positive this week. Tuesday my hcg was only 41.5 so I initially thought this was another chemical but they assured me i was just really early and to go again Thursday which I did... it was 177! So it more than quadrupled in 48 hours (actually 47.5, I went a little earlier on Thursday)

They said they like to see it roughly double every 48 hours.... but mine more than quadrupled- what does this mean?!