Do not understand the model

on monday, he said he gave peter 5/6 of his marbles. this means that originally he had 6 units of marbles but he gave 5 units away so he is left with only 1 unit of marble. then he bought another 15 marbles so we draw another box behind to represent the 15 marbles.
the 1 unit and the additional 15 marbles represent the original amount of marbles he had on tuesday before anything happened.

then he said he lost 2/3 of his marbles so we represent his original amount of marbles on tuesday as 3 units. now, after losing his marbles, his is left with only 1 unit. then he said he bought double the amount he bought on monday which means that he bought 30 marbles so we draw another box representing the additional 30 marbles.

after that the question said he was left with 39 marbles in the end which means the 1 unit and additional 30 marbles is equals to the 39 marbles