Comment by gregoriol

It's always nice to have a (very) little intro, but both of these have a bad subscript.

The first one says I know it won't take you long, but that assumes you know the time it'll take me to handle whatever you are going to say, but the reality is that you likely don't know, and even if the conversation itself lasts less than a minute, the person will likely been cut of what they were doing for more than this.

The second one is even worse as you imply that you know are bothering me, so don't bother me! (even if it is a polite phrase, it's not nice)

In other words, just ask. It's more efficient and doesn't make any assumption: we'll figure out how long it takes and if that bothers me.