It is a matter of liquidity. A cost channel of 1BTC might solely switch at most 1BTC  in every course.
Let’s take an instance: Alice and Bob have a 1BTC cost channel:
Alice <- 1BTC -> Bob
There may be 1 bitcoin locked within the channel. Funds are crucial on one facet or the opposite. As an example, for instance Alice unilaterally funded the channel. In the beginning, she’ll have all funds on her facet:
Alice Bob ----- --- 1 BTC 0 BTC
Now if she pays Bob, the quantity of funds locked within the channel is not going to change. She essentially sends some from her facet to the opposite:
Alice Bob ----- --- 1 BTC 0 BTC 0.9 BTC 0.1 BTC
If Bob is promoting stuff and getting paid in BTC by way of this channel (whether or not it’s Alice paying him or another person routing their funds by way of Alice‘s channel with Bob), Bob will are inclined to get all of the channel funds on his facet of the channel over time:
Alice Bob ----- --- 1 BTC 0 BTC 0.9 BTC 0.1 BTC 0.6 BTC 0.4 BTC 0.7 BTC 0.3 BTC 0.1 BTC 0.9 BTC 0 BTC 1 BTC
At this level Bob can not obtain funds from this channel anymore. He can shut the channel to withdraw onchain his 1BTC. That is what the textual content you quote is referring to. We are able to say Bob “bundled” a lot of small incoming cost in a single onchain transaction transferring a complete BTC.
 Conceptually. Technically, it is lower than that.