You’ve basically answered your own question. When some mentions drip-feeding links they simply mean building links slower over time instead of all at once.
Say you buy 100 backlinks from backlinks generator, they can drip feed/schedule these say over the next 30 days, like 3-4 links a day until all 100 links are built.
example:
If you buy a Pro plan of 5000 Backlinks Links and set the drip feed for the next 30 days, so we will build 167 backlinks per day for the next 30 days until the link building process is completed.
Total number of links ÷ Drip-feed number of days = Daily built backlinks
Drip-feed formula
The reason drip feeding is important is that you want to keep your link velocity consistent and going from no links the past few weeks/months to say 5000 in a single day doesn’t look natural. That’s why always choose the drip-feed cause it’s free in Backlinks Generator.