Explain ATX efile code language

[Margaret CPA in OH]

I have 5 1099 transmissions since January. All say Transmitted to EFC in the status column. When I checked on the status of these at the ATX site, 2 show that they have been sent to IRS but not received the IRS Ack but have been "Accepted." One shows "Accepted" but not yet sent to IRS or IRS ack'ed. This last one was transmitted to EFC on Jan. 22.

I, obviously incorrectly, thought that "Accepted" was IRS accepted. Apparently not. Is it clear to others that IRS ack does not equal Accepted and that Accepted does not equal IRS ack? What does Accepted mean, then? And why this inordinate delay with these 1099's? My 1040 are whizzing through!