Rocket tally from IDF much lower than from Gaza groups

As of this morning, the IDF says that 2600 rockets had been fired from Gaza to Israel.

Hamas claims to have fired 2090 rockets.

Islamic Jihad claims to have fired 2039 rockets.

Al Aqsa Martyrs Brigade hasn't added them all up but they have fired about 10 a day, and the PRC perhaps 5 a day. Other groups also claim a number of rockets a day.

There is nearly a 2000 rocket gap.

How to explain this?

Are the terror groups exaggerating? I'm sure that there is some of that.  But their counts are very precise by rocket type.

Is the IDF lying? They have no incentive to lie to minimize the rocket threat.

The terror groups seem to count mortars, and I'm not sure if the IDF does. That would account for quite a few.

My guess is that there are a lot of rockets that are blowing up on at the launchpad, some are being double-counted from joint operations, and hundreds are falling short in Gaza, injuring and killing many - like the ones that killed kids in Shati and Shifa yesterday.

If only there were credible, objective observers in Gaza who could tell us what is going on instead of parroting Hamas talking points.